The Bible Answer:
God appeared in the flesh, justified Himself in the Spirit, showed Himself to the Angels, preached to the nations, accepted by faith in the world, was exalted in glory. (1 Timothy 3:16)
This is the true God and eternal life (1 John 5:20).
“Behold, the Virgin in her womb will receive and give birth to a Son, and they will call His name Immanuel, which means: God is with us”. (Holy Gospel of Matthew 1:23)
And fear seized everyone, and they glorified God, saying: A great prophet has risen up between us, and God has visited His people. This opinion of Him spread throughout Judea and all the surrounding area. (Luke 7: 16-17)
For a baby was born to us – a Son was given to us; dominion on His shoulders, and they will call His name: Wonderful, Counselor, Mighty God, Father of Eternity, Prince of Peace. (Isaiah 9: 6)
But the word that you hear is not Mine, but the Father’s who sent Me. (Holy Gospel of John 14:24)
And he who sees Me sees Him who sent Me. (Holy Gospel of John 12:45)
whoever receives Me, receives Him who sent Me … (Holy Gospel of Matthew 10:40)

What to do?
So they said to Him, What should we do to do the works of God?
Jesus answered and said to them: This is the work of God, so that you believe in Him whom He sent. (Holy Gospel of John 6: 28,29)
Truly, truly, I say to you, he who hears My word and believes in Him who sent Me has eternal life and does not come into judgment, but has passed from death to life. (Holy Gospel of John 5:24)
and, leading them out, said: my lords! what should I do to be saved? But they said, Believe in the Lord Jesus Christ, and you and all your house will be saved. (Acts of the Holy Apostles 16: 30,31)
Then Jesus said to the Jews who believed in Him: if you abide in My word, then you are truly My disciples, and you will know the truth, and the truth will make you free. (John 8: 31-32)
He answered and said to them: My mother and my brothers are those who listen to the word of God and do it. (Luke 8:21)
What you have learned, what you have received and heard and seen in me, do it, and the God of peace will be with you. (Philippians 4: 9)
But he answered and said to him who had spoken: Who is my mother? and who are my brothers? And, pointing with His hand to His disciples, He said: Behold my mother and My brothers; for whoever will do the will of my Father in Heaven, the same is my brother and sister and mother. (Matthew 12: 48-50)
The will of the Father who sent Me is that of what He gave Me, nothing to destroy, but to resurrect everything on the last day.
This is the will of Him who sent Me, that everyone who sees the Son and believes in Him may have eternal life; and I will raise him up on the last day. (Holy Gospel of John 6: 39,40)
Know therefore, all the house of Israel, that God has made this Jesus, whom you crucified, both Lord and Christ.
Hearing this, they were moved by heart and said to Peter and the other Apostles: what should we do, brothers?
Peter said to them: Repent, and let each of you be baptized in the name of Jesus Christ for the remission of sins; and receive the gift of the Holy Ghost.
For the promise belongs to you and to your children and to all who are far off, whoever the Lord our God will call.
And in many other words he testified and exhorted, saying: Save yourself from this perverse generation. (Acts of the Holy Apostles 2: 36-40)

Peter’s sermon:
Peter opened his mouth and said: Truly I know that God is impartial,
but in every nation he who fears him and works righteousness is pleasing to him.
He sent a word to the children of Israel, preaching peace through Jesus Christ; This is the Lord of all.
You know what happened throughout Judea, starting from Galilee, after the baptism preached by John:
how God anointed Jesus of Nazareth with the Holy Spirit and power, and He walked doing good and healing all who were oppressed by the devil, because God was with Him.
And we are witnesses of everything that He did in the land of Judah and in Jerusalem, and that at last they killed Him by hanging Him on a tree.
This God raised up on the third day, and made Him appear
not to all the people, but to witnesses, chosen by God, to us, who ate and drank with Him, after His resurrection from the dead.
And He commanded us to preach to people and testify that He is the Judge of the living and the dead determined by God.
All the prophets testify to Him that everyone who believes in Him will receive the remission of sins by His name.
So repent and be converted, that your sins may be blotted out,
may times of joy come from the presence of the Lord, and may He send Jesus Christ, destined for you … (Acts of the Holy Apostles 3: 19,20)

What’s next?
And this gospel of the kingdom will be preached in all the world as a testimony to all nations; and then the end will come. (Holy Gospel of Matthew 24:14)
Whoever believes and is baptized will be saved; but whoever does not believe will be condemned. (Holy Gospel of Mark 16:16)

The second coming of Jesus Christ and the resurrection of the righteous and unrighteous:
And they said, Men of Galilee! why are you standing and looking at the sky? This Jesus, ascended from you into heaven, will come in the same way as you saw Him ascending into heaven. (Acts of the Apostles 1:11)
The sun will turn to darkness and the moon to blood before the great and glorious day of the Lord comes. (Joel 2:31, Acts of the Holy Apostles 2:20)
then the sign of the Son of Man will appear in heaven; and then all the tribes of the earth will mourn