Believe it or not, there is absolutely no mention of humans existing before their births. I’ve read the Bible from Genesis to Revelation twenty times and nowhere was there a mention of us existing prior to our conception.
People who believe in reincarnation often claim to be somebody important in a supposed previous life. They somehow get a vague idea of being in a certain place before and their over-active imaginations fill in the details.
The only being in the universe who existed before his birth was Jesus Christ. He obliquely mentioned this in John 8:56 (BBE) when he said to the Pharisees, “Your father Abraham was full of joy at the hope of seeing my day: he saw it and was glad.”
Mocking his apparent mistake in claiming that Abraham saw his appearance on this planet, the Pharisees asked in verse 57, “Then the Jews said to him, ‘You are not fifty years old; have you seen Abraham?'”
Our Lord hinted at his pre-existence in verse 58. Jesus said to them, Truly I say to you, Before Abraham came into being, I am.'” Those final words, “I am,” was the holy and unspeakable name of God Almighty. That’s why the Pharisees picked up stones to stone him to death. His time hadn’t come yet so he slipped through the crowd of enraged religionists. They knew what Exodus 3:13 and 14 said about what God’s name was.”And Moses said unto God, ‘Behold, when I come unto the children of Israel, and shall say unto them, “The God of your fathers hath sent me unto you;” and they shall say to me, “What is his name?” what shall I say unto them?’ And God said unto Moses, ‘I AM THAT I AM:’ and he said, ‘Thus shalt thou say unto the children of Israel, I AM hath sent me unto you.'”
I once joined an errant house church, unaware that it was a cult. Its lay minister taught many blasphemous doctrines, one of which was that we existed as space aliens before we were born into human bodies. Check out my book, How I Was Razed, at Amazon and discover how wonderfully the Lord freed me.