Messenger of Allah, my father is very old. There is an old obligation of Hajj upon him from Allah, but he is not capable of sitting on the back of the camel. Thereupon Allah's Apostle ﷺ said: Perform Hajj on his behalf.
يَا رَسُولَ اللَّهِ إِنَّ أَبِي شَيْخٌ كَبِيرٌ عَلَيْهِ فَرِيضَةُ اللَّهِ فِي الْحَجِّ وَهُوَ لاَ يَسْتَطِيعُ أَنْ يَسْتَوِيَ عَلَى ظَهْرِ بَعِيرِهِ فَقَالَ النَّبِيُّ ﷺ فَحُجِّي عَنْهُ