The Prophet ﷺ said, "When one of you leads the people in prayer, let him make it brief, for among them are the sick, the weak, and the elderly. But when one of you prays alone, let him prolong it as much as he wishes."
أخبرنا قتيبة عن مالك عن أبي الزناد عن الأعرج
عن النبي ﷺ قال إذا صلى أحدكم بالناس فليخفف فإن فيهم السقيم والضعيف والكبير فإذا صلى أحدكم لنفسه فليطول ما شاء
Bukhari transmitted it in the Book of Adhan, Chapter "If He Prays Alone He May Lengthen It As He Wishes," no. 703, from the hadith of Malik, by this chain, and it is in Muwatta (Yahya): 1/134, and in Kubra, no. 897.Muslim also transmitted it, no. 467, through another route from Abu Zinad, by this chain.