How can I know this?
There are many truths to support this but I'm just addressing a few.
The empty tomb is the first place to start.
Second, prophecy from the Old Testament covenant of repetitive animal sacrifice fulfilled in the New Testament covenant of Christ, the once and for all time sacrificial Lamb.
Thirdly, the truth of His return outlined in the yet to be fulfilled book of Revelation.
The bible speaks through divine authority, having been inspired by the Holy Spirit.
God is seen in creation so that man can not deny without penalty.
There will be no excuse!
Background
I will put enmity between you and the woman, and between your offspring and her offspring; he shall bruise your head, and you shall bruise his heel." - Genesis 3:15
Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel. - Isaiah 7:14
34 And Mary said to the angel, "How will this be, since I am a virgin?"
35 And the angel answered her, "The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy-the Son of God. - Luke 1:34-35
But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, - Galatians 4:4
14 Since therefore the children share in flesh and blood, he himself likewise partook of the same things, that through death he might destroy the one who has the power of death, that is, the devil,
15 and deliver all those who through fear of death were subject to lifelong slavery. - Hebrews 2:14-15
The empty tomb
1 But on the first day of the week, at early dawn, they went to the tomb, taking the spices they had prepared.
2 And they found the stone rolled away from the tomb,
3 but when they went in they did not find the body of the Lord Jesus.
4 While they were perplexed about this, behold, two men stood by them in dazzling apparel.
5 And as they were frightened and bowed their faces to the ground, the men said to them, "Why do you seek the living among the dead?
6 He is not here, but has risen. Remember how he told you, while he was still in Galilee,
7 that the Son of Man must be delivered into the hands of sinful men and be crucified and on the third day rise." - Luke 24:1-7
18 "See, we are going up to Jerusalem. And the Son of Man will be delivered over to the chief priests and scribes, and they will condemn him to death
19 and deliver him over to the Gentiles to be mocked and flogged and crucified, and he will be raised on the third day." - Matthew 20:18-19
21 And he strictly charged and commanded them to tell this to no one,
22 saying, "The Son of Man must suffer many things and be rejected by the elders and chief priests and scribes, and be killed, and on the third day be raised." - Luke 9:21-22
Repeated blood sacrifice replaced by once for all
1 For since the law has but a shadow of the good things to come instead of the true form of these realities, it can never, by the same sacrifices that are continually offered every year, make perfect those who draw near.
2 Otherwise, would they not have ceased to be offered, since the worshipers, having once been cleansed, would no longer have any consciousness of sins?
3 But in these sacrifices there is a reminder of sins every year.
4 For it is impossible for the blood of bulls and goats to take away sins.
5 Consequently, when Christ came into the world, he said, "Sacrifices and offerings you have not desired, but a body have you prepared for me;
6 in burnt offerings and sin offerings you have taken no pleasure.
7 Then I said, 'Behold, I have come to do your will, O God, as it is written of me in the scroll of the book.'"
8 When he said above, "You have neither desired nor taken pleasure in sacrifices and offerings and burnt offerings and sin offerings" (these are offered according to the law),
9 then he added, "Behold, I have come to do your will." He does away with the first in order to establish the second.
10 And by that will we have been sanctified through the offering of the body of Jesus Christ once for all.
11 And every priest stands daily at his service, offering repeatedly the same sacrifices, which can never take away sins.
12 But when Christ had offered for all time a single sacrifice for sins, he sat down at the right hand of God,
13 waiting from that time until his enemies should be made a footstool for his feet.
14 For by a single offering he has perfected for all time those who are being sanctified.
15 And the Holy Spirit also bears witness to us; for after saying,
16 "This is the covenant that I will make with them after those days, declares the Lord: I will put my laws on their hearts, and write them on their minds,"
17 then he adds, "I will remember their sins and their lawless deeds no more."
18 Where there is forgiveness of these, there is no longer any offering for sin. - Hebrews 10:1-18
6 In sacrifice and offering you have not delighted, but you have given me an open ear. Burnt offering and sin offering you have not required.
7 Then I said, "Behold, I have come; in the scroll of the book it is written of me:
8 I delight to do your will, O my God; your law is within my heart." - Psalm 40:6-8
He is coming
6 Then I heard what seemed to be the voice of a great multitude, like the roar of many waters and like the sound of mighty peals of thunder, crying out, "Hallelujah! For the Lord our God the Almighty reigns.
7 Let us rejoice and exult and give him the glory, for the marriage of the Lamb has come, and his Bride has made herself ready;
8 it was granted her to clothe herself with fine linen, bright and pure"- for the fine linen is the righteous deeds of the saints.
9 And the angel said to me, "Write this: Blessed are those who are invited to the marriage supper of the Lamb." And he said to me, "These are the true words of God."
10 Then I fell down at his feet to worship him, but he said to me, "You must not do that! I am a fellow servant with you and your brothers who hold to the testimony of Jesus. Worship God." For the testimony of Jesus is the spirit of prophecy. - Revelation 19:6-10
11 Then I saw heaven opened, and behold, a white horse! The one sitting on it is called Faithful and True, and in righteousness he judges and makes war.
12 His eyes are like a flame of fire, and on his head are many diadems, and he has a name written that no one knows but himself.
13 He is clothed in a robe dipped in blood, and the name by which he is called is The Word of God.
14 And the armies of heaven, arrayed in fine linen, white and pure, were following him on white horses.
15 From his mouth comes a sharp sword with which to strike down the nations, and he will rule them with a rod of iron. He will tread the winepress of the fury of the wrath of God the Almighty.
16 On his robe and on his thigh he has a name written, King of kings and Lord of lords.
17 Then I saw an angel standing in the sun, and with a loud voice he called to all the birds that fly directly overhead, "Come, gather for the great supper of God,
18 to eat the flesh of kings, the flesh of captains, the flesh of mighty men, the flesh of horses and their riders, and the flesh of all men, both free and slave, both small and great."
19 And I saw the beast and the kings of the earth with their armies gathered to make war against him who was sitting on the horse and against his army.
20 And the beast was captured, and with it the false prophet who in its presence had done the signs by which he deceived those who had received the mark of the beast and those who worshiped its image. These two were thrown alive into the lake of fire that burns with sulfur.
21 And the rest were slain by the sword that came from the mouth of him who was sitting on the horse, and all the birds were gorged with their flesh. - Revelation 19:11-21
Judgment
11 Then I saw a great white throne and him who was seated on it. From his presence earth and sky fled away, and no place was found for them.
12 And I saw the dead, great and small, standing before the throne, and books were opened. Then another book was opened, which is the book of life. And the dead were judged by what was written in the books, according to what they had done.
13 And the sea gave up the dead who were in it, Death and Hades gave up the dead who were in them, and they were judged, each one of them, according to what they had done.
14 Then Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire.
15 And if anyone's name was not found written in the book of life, he was thrown into the lake of fire. - Revelation 20:11-15
All things new
1 Then I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and the sea was no more.
2 And I saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband.
3 And I heard a loud voice from the throne saying, "Behold, the dwelling place of God is with man. He will dwell with them, and they will be his people, and God himself will be with them as their God.
4 He will wipe away every tear from their eyes, and death shall be no more, neither shall there be mourning, nor crying, nor pain anymore, for the former things have passed away."
5 And he who was seated on the throne said, "Behold, I am making all things new." Also he said, "Write this down, for these words are trustworthy and true."
6 And he said to me, "It is done! I am the Alpha and the Omega, the beginning and the end. To the thirsty I will give from the spring of the water of life without payment.
7 The one who conquers will have this heritage, and I will be his God and he will be my son.
8 But as for the cowardly, the faithless, the detestable, as for murderers, the sexually immoral, sorcerers, idolaters, and all liars, their portion will be in the lake that burns with fire and sulfur, which is the second death." - Revelation 21:1-8
The end
1 Then I saw an angel coming down from heaven, holding in his hand the key to the bottomless pit and a great chain.
2 And he seized the dragon, that ancient serpent, who is the devil and Satan, and bound him for a thousand years,
3 and threw him into the pit, and shut it and sealed it over him, so that he might not deceive the nations any longer, until the thousand years were ended. After that he must be released for a little while. - Revelation 20:1-3
and the devil who had deceived them was thrown into the lake of fire and sulfur where the beast and the false prophet were, and they will be tormented day and night forever and ever. - Revelation 20:10
Final words
11 Let the evildoer still do evil, and the filthy still be filthy, and the righteous still do right, and the holy still be holy."
12 "Behold, I am coming soon, bringing my recompense with me, to repay each one for what he has done.
13 I am the Alpha and the Omega, the first and the last, the beginning and the end." - Revelation 22:11-13
16 "I, Jesus, have sent my angel to testify to you about these things for the churches. I am the root and the descendant of David, the bright morning star."
17 The Spirit and the Bride say, "Come." And let the one who hears say, "Come." And let the one who is thirsty come; let the one who desires take the water of life without price. - Revelation 22:16-17
