ENOfficial
Asmar b. Mudarris told that when he came and swore allegiance to the Prophet (ﷺ) he said, “If anyone comes to water, no Muslim having come to it before him, it belongs to him.” Abu Dawud transmitted it.
Source: sunnah.com
Other translations
Arabic
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
sunnah.com