Mt 7:21, Jn 6:40, 1 Jn 5:1, Jn 5:39, Jn 20:31, Jn 3:16
Only those who do the Father's will can enter the kingdom of heaven. That is, only those who believe in Jesus as the Christ can enter the kingdom of heaven. (Mt 7:21, Jn 6:40, 1 Jn 5:1)
Mt 7:21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
Jn 6:40 And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
1 Jn 5:1 Whosoever believeth that Jesus is the Christ is born of God: and every one that loveth him that begat loveth him also that is begotten of him.
God gave us the Old and New Testaments so that we might believe that Jesus is the Christ. (Jn 5:39, Jn 20:31)
Jn 5:39 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
Jn 20:31 But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.
In order to save us, God sent His only begotten son to this earth to do the work of Christ, and He gave eternal life to those who believe in it. (Jn 3:16)
Jn 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.