Mishkat al-Masabih 11 Business Transactions كتاب البيوع 236

وَعَنْ أَسْمَرَ بْنِ مُضَرِّسٍ قَالَ: أَتَيْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَبَايَعْتُهُ فَقَالَ: «مَنْ سَبَقَ إِلَى مَاءٍ لَمْ يَسْبِقْهُ إِلَيْهِ مُسْلِمٌ فَهُوَ لَهُ» . رَوَاهُ أَبُو دَاوُد

Asmar b. Mudarris told that when he came and swore allegiance to the Prophet he said, “If anyone comes to water, no Muslim having come to it before him, it belongs to him.” Abu Dawud transmitted it.