Qaloo lam naku mina almusalleen (surah Muddathir: 43)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(74:43) They will answer: 'We were not among those who observed Prayer, *33

Qaaloo lam naku minal musalleen

*33) That is, "We were not of those who after having believed in Allah and His Messenger and His Boo , performed the foremost duty imposed by Allah, i.e. the Prayer. " Here, it should be understood well that unless a person has believed he cannot offer the Prayer at all. Therefore, one's being of those who performed the Prayer, by itself implies that one is a believer. But by attributing one's going to Hell to one's not being of those who performed their Prayer, it has been made explicit that one cannot escape Hell even after having believed if one dces not perform one's Prayers regularly.