وَيَجِبُ طَلَبُهُ مِمَّنْ هُوَ مَعَهُ ... وَإِنْ لَمْ يُعْطِهِ إِلَّا بِثَمَنِ مِثْلِهِ لَزِمَهُ شِرَاؤُهُ بِهِ إِنْ كَانَ مَعَهُ فَاضِلًا عَنْ نَفَقَتِهِ
When the situation is one in which people normally share water, the person must ask those with them. If water is offered only at a fair equivalent price, buying it is required when the person has funds beyond necessary expenses. Excessive pricing or lack of spare funds removes that obligation.