"If any of you leads the people in prayer, let him shorten it, because among them are the weak, the sick, and the busy (who have needs to fulfill). If any of you prays alone, then let him prolong (his prayer) as much as he wishes."[Al-Bukhari]

عن أبي هريرة -- مرفوعًا: «إذا صلى أحدكم للناس فَلْيُخَفِّفْ فإن فيهم الضعيف والسَّقِيمَ وذَا الحاجة، وإذا صلى أحدكم لنفسه فَلْيُطَوِّلْ ما شاء». (البخاري)