Sahih Muslim , Book 5, Hadith 302 (In-Book) ⓘ

Abu Dharr reported: The Messenger of Allah said to me: O Abu Dharr, you would soon find after me rulers who would make their prayers dead. You should say prayer at its prescribed time. If you say prayer at its prescribed time that would be a supererogatory prayer for you, otherwise you saved your prayer.

حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا جَعْفَرُ بْنُ سُلَيْمَانَ، عَنْ أَبِي عِمْرَانَ الْجَوْنِيِّ، عَنْ عَبْدِ اللَّهِ بْنِ الصَّامِتِ، عَنْ أَبِي ذَرٍّ، قَالَ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ يَا أَبَا ذَرٍّ إِنَّهُ سَيَكُونُ بَعْدِي أُمَرَاءُ يُمِيتُونَ الصَّلاَةَ فَصَلِّ الصَّلاَةَ لِوَقْتِهَا فَإِنْ صَلَّيْتَ لِوَقْتِهَا كَانَتْ لَكَ نَافِلَةً وَإِلاَّ كُنْتَ قَدْ أَحْرَزْتَ صَلاَتَكَ ‏" ‏ ‏.‏