"I met a man who accompanied the Prophet ﷺ as Abu Hurairah (may Allah be pleased with him), accompanied him for four years. He said: 'The Messenger of Allah ﷺ forbade any one of us to comb his hair each day,[1] or to urinate in the place where he performs Ghusl, or for a man to perform Ghusl using the leftover water of a women, or a woman to perform Ghusl using the leftover water of a man - they should scoop it out together.'" [1] It is said this is to prevent him from making his physical appearance his main aim. (Using translation from Nasāʾī 238)  

لَقِيتُ رَجُلًا صَحِبَ النَّبِيَّ ﷺ كَمَا صَحِبَهُ أَبُو هُرَيْرَةَ أَرْبَعَ سِنِينَ قَالَ «نَهَى رَسُولُ اللهِ ﷺ أَنْ يَمْتَشِطَ أَحَدُنَا كُلَّ يَوْمٍ أَوْ يَبُولَ فِي مُغْتَسَلِهِ أَوْ يَغْتَسِلَ الرَّجُلُ بِفَضْلِ الْمَرْأَةِ أَوِ الْمَرْأَةُ بِفَضْلِ الرَّجُلِ وَلْيَغْتَرِفَا جَمِيعًا»