'Enter' in the Bible

Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?

Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.

I am the door: by me if any man enter in, he shall be saved, and shall go in and out, and find pasture.