Sahih al-Bukhari 1868

Abu Maamar narrated to us; Abd al-Warith narrated to us, from Abu al-Tayyah, from Anas (may Allah be pleased with him), who said: When the Prophet arrived in Medina, he ordered that a mosque be built. He said: Banu Najjar, set a price for it for me. They replied: We seek its price from Allah alone. He ordered the graves of the polytheists to be dug up, and they were exhumed. Then he ordered the ruins to be leveled and the palm trees to be cut down. The palm trunks were set in rows toward the qibla of the mosque.