In Sunan al-Nasaa’i (5570) it is narrated that Ibn al-Daylami said to ‘Abd-Allaah ibn ‘Amr, “O ‘Abd-Allaah ibn ‘Amr, did you hear the Messenger of Allaah (peace and blessings of Allaah be upon him) say anything about wine?” He said, “Yes, I heard the Messenger of Allaah (peace and blessings of Allaah be upon him) say, ‘If any man from among my ummah drinks wine, Allaah will not accept his prayers for forty days.’” This was classed as saheeh by al-Albaani in al-Silsilat al-Saheehah (709). What this means is that he will not be rewarded for them, but he is still obliged to pray; in fact he is obliged to do all the prayers. If he forsakes prayer during this time, he will be committing one of the worst of major sins, one which some of the scholars said amounts to kufr, Allaah forbid.