What is the ruling on one who deliberately abandoned prayer for years due to laziness, and now wishes to return and commit? Does he have to make up the prayers he missed, or does he simply repent and commit to the current prayers only? And can he renew his Islam to waive the missed prayers?

Abandoning prayer is a grave sin; in fact, some scholars consider it an act of disbelief. Missing even one prayer is worse than fornication, theft, consuming alcohol, and taking a life. One must repent to Allah and maintain prayer. As for the prayers that were missed, there is a difference of opinion among scholars regarding the obligation to make them up (qada'). The more cautious approach is to make them up, but there is no harm in following those who believe that making them up is not obligatory, and that sincere repentance combined with abundant voluntary prayers is sufficient, provided that one commits to observing prayers and does not neglect them again.