Sunan an-Nasa'i — The Book of the Masjids — Hadith No: 701
Translation
It was narrated that Talq bin 'Ali said:"We went out as a delegation to the Prophet (ﷺ); we gave him our oath of allegiance and prayed with him. We told him that in our land there was a church that belonged to us. We asked him to give us the leftovers of his purification (Wudu' water). So he called for water, performed Wudu' and rinsed out his mouth, then he poured it into a vessel and said to us: 'Leave, and when you return to your land, demolish your church, and sprinkle this water on that place, and take it as a Masjid.' We said: 'Our land is far away and it is very hot; the water is far away and it is very hot; the water will dry up.' He said: 'Add more water to it, for that will only make it better.' So we left and when we came to our land we demolished our church, then we sprinkled the water on that place and took it as a Masjid, and we called the Adhan in it. The monk was a man from Tayy', and when he heard the Adhan, he said: 'It is a true call.' Then he headed toward one of the hills and we never saw him again