What is the ruling on missed prayers for someone who stopped praying then returned to their Lord? Can they be made up quickly if one fears death? Does a prayer in the mosque, which equals 25 prayers, compensate for 25 missed prayers?

Congregational prayer is twenty-five degrees better than individual prayer, and this does not mean that it suffices for 25 previous prayers. Scholars have differed regarding making up prayers intentionally missed. The majority opinion is that it is obligatory to make them up, and they cite the hadith: "Allah's debt is more worthy of being fulfilled," and by analogy a fortiori to making up prayers by one who slept through them or forgot them. Others, including Ibn Taymiyyah, held that it is not obligatory to make them up, arguing that prayer is "a book prescribed at fixed times," and that making up prayers requires a new command which has not been transmitted concerning one who intentionally missed them. The authoritative fatwa is that it is obligatory to make them up. Therefore, one who intentionally misses prayers must calculate what he missed and make them up. As for the opinion of Shaykh al-Islam, he must make sincere repentance and perform abundant supererogatory prayers.