A shaykh of Banu Zuhrah narrates from Sayyiduna Umar (may Allah be pleased with him) that he wrote to Sayyiduna Sa'd (may Allah be pleased with him) to grant Sayyiduna Sa'id bin Zayd (may Allah be pleased with him) some land, so he granted him the land of Banu al-Raqil. Ibn al-Raqil came to Sayyiduna Umar (may Allah be pleased with him) and said: O Commander of the Believers! On what terms did you make peace with us? He said: That you pay the jizyah, and your land, wealth and children remain with you. He said: O Commander of the Believers! Have you given my land to Sa'id bin Zayd? So Sayyiduna Umar (may Allah be pleased with him) wrote to Sayyiduna Sa'd (may Allah be pleased with him): Return his land to him. Then he invited him to Islam and he became Muslim; Sayyiduna Umar (may Allah be pleased with him) fixed a stipend of seven hundred for him, placed his stipend among the tribe of Khath'am, and said: If you stay on your land, keep paying as much as you used to pay.
There is weakness in its chain.
(b) If it is established, then this saying, "and your land remains yours," means "the land which you cultivate and on which you pay the tax," and this land had been taken from them by force. Note that even after his becoming Muslim the kharaj did not end, whereas in land of a peace treaty it drops.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18415