Hadithcore
Mishkat al-Masabih, 3002

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.

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

References1 variant
In-Book Reference
Book 11, Hadith 236