Abu Iyad narrates from Sayyiduna Umar (may Allah be pleased with him): Do not buy slaves from a dhimmi, for they are people who pay jizyah, some of them paying on behalf of others; and do not buy their lands either. Why should any of you put himself into humiliation when Allah, the Lord of Might, has saved him from it?
Abu Ubayd said: In our view, what he meant is that when a dhimmi has slaves, land and visible wealth, his jizyah is greater, and the practice of Sayyiduna Umar (may Allah be pleased with him) was to fix the jizyah on them according to their ease and hardship. For this reason he disliked buying their slaves. As for buying the land, he had the kharaj in view: he disliked that this kharaj should fall upon the Muslims. Do you not see that he says: Let none of you put himself into humiliation when Allah has saved him from it? After Sayyiduna Umar (may Allah be pleased with him), senior Companions, among them Sayyiduna Abdullah bin Mas'ud, who had land in Radhan, and Khabbab bin al-Aratt (may Allah be pleased with them both), and others, granted a concession in this matter.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18400
Qatadah (may Allah have mercy on him) narrates from Sayyiduna Ali (may Allah be pleased with him) that he disliked buying anything of kharaj land, and he would say: The kharaj of the Muslims is due on it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18401
Kulayb bin Wa'il said: I said to Sayyiduna Abdullah bin Umar (may Allah be pleased with them both): I have bought land. He said: Buying land is good. He said: I said: I pay a dirham and a qafiz (a measure) of food for every jarib of land. He said: Do not put humiliation around your neck.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18402