What is the ruling on the marriage contract for a young man who prayed intermittently before and after the contract, and then repented?

Praise be to Allah for your repentance. Intentionally delaying a prayer beyond its prescribed time is a grave sin by consensus. What is held as authoritative for us is the obligation to make up intentionally missed prayers. You are not required to renew your marriage contract, even if you entered into it while you were not praying, because the one who abandons prayer out of laziness is not considered an apostate by the majority of scholars.