Imagine someone who knows almost nothing about Christianity asks you what Christians believe, but instead of giving them a book, you can give them just three passages of Scripture to read.
Which three would you choose?
There are no restrictions on length. You could choose a single verse, a parable, an entire chapter, or a longer passage.
Of course, John 3:16-18
“For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. For God did not send his Son into the world to condemn the world, but in order that the world might be saved through him. Whoever believes in him is not condemned, but whoever does not believe is condemned already, because he has not believed in the name of the only Son of God.”
Why? Because there is no other way. Jesus Himself told us.
“Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.” John 14:6
Why? Because Jesus IS God.
“Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am.” “In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by him; and without him was not any thing made that was made.” And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth."
There are more, but I feel this is a good place to start.
Peter
Eph 4:13 Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:
2Co 5:15 And that he died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again.
1Th 4:17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.