The last instruction the Prophet ﷺ gave me was, "Keep your prayer brief, and gauge the people by the weakest among them, for among them are the young, the old, the frail, and the one with a pressing need."
قال وكان آخر شيء عهده النبي ﷺ إلي أن قال جوز في صلاتك واقدر الناس بأضعفهم فإن منهم الصغير والكبير والضعيف وذا الحاجة
No references are available.
Its isnad is sahih, mentioned previously at 16226.