The Prophet ﷺ used to pray so much that his feet used to become edematous or swollen, and when he was asked as to why he prays so much, he would say, "Shall I not be a thankful slave (to Allah)?"

كَانَ النَّبِيُّ ﷺ يُصَلِّي حَتَّى تَرِمَ أَوْ تَنْتَفِخَ قَدَمَاهُ فَيُقَالُ لَهُ فَيَقُولُ أَفَلاَ أَكُونُ عَبْدًا شَكُورًا