ذِكْرُ الْأَمْرِ لِلْمَرْءِ إِذَا صَلَّى وَحْدَهُ أَنْ يُطَوِّلَ مَا شَاءَ فِيهَا
When one of you leads the people in prayer, he should be brief, for among them are the weak, the sick, and the aged. But when one of you prays by himself, he may pray as long as he likes. (Using translation from Abū Dāʾūd 794)
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ «إِذَا صَلَّى أَحَدُكُمْ بِالنَّاسِ فَلْيُخَفِّفْ فَإِنَّ فِيهِمُ السَّقِيمَ وَالضَّعِيفَ وَالْكَبِيرَ وَإِذَا صَلَّى أَحَدُكُمْ لِنَفْسِهِ فَلْيُطَوِّلْ مَا شَاءَ»