Nahj al-Balāgha
Hadith 1018وَكَانَ رَسُولُ اللهِ (صلى الله عليه وآله) نَصِباً بِالصَّلاَةِ بَعْدَ التَّبْشِيرِ لَهُ بِالْجَنَّةِ، لِقَوْلِ اللهِ سُبْحَانَهُ: ﴿وَأْمُرْ أَهْلَكَ بِالصَّلَاةِ وَاصْطَبِرْ عَلَيْهَا﴾، فَكَانَ يَأُمُرُ بِهَا أَهْلَهُ وَيَصْبِرُ عَلَيْهَا نَفْسَهُ.
Even after receiving assurance of Paradise, the Messenger of Allāh - peace and blessing of Allāh be upon him and his descendants - used to exert himself for prayers because of Allāh, the Glorified’s command: “And enjoin prayer on thy followers, and adhere thou steadily unto it, ...” (Qur’ān, 20:132). Then the Holy Prophet used to enjoin his followers to prayer and exert himself for it.