John 3 says, “I tell you most solemnly, unless a man be born through water and the spirit, he cannot enter the kingdom of God; what is born of the flesh is flesh; what is born of the spirit is spirit.”
You could ask them to explain John 3 to you.
The whole verse of the quote in Ps 49 is:
But man could never redeem himself or pay his ransom to God:
it costs so much to redeem his life, it is beyond him;
how then could he live on for ever and never see the Pit—
What is in red, the psalmist says is that he will get the same treatment as all the evil people do, because he can’t be redeemed either. But then he knows that this is not fair or just. So he comes to this conclusion in verse 15, “But God will redeem my life from the grasp of Sheol, and will receive me”.
This is all to hint at the final resurrection and life eternal.
And Psalm 79 says:
“Bring us back, O God of hosts: let your face shine on us and we shall be saved.”