Sayyiduna Ali (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) said: "The protection (dhimmah) of the Muslims is one; even the lowest of them is equal in it. Whoever violates the protection given by a Muslim, upon him is the curse of Allah, the angels and all the people, and none of his worship, neither voluntary nor obligatory, will be accepted."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16812
Qays bin Ubad (may Allah have mercy on him) said: Al-Ashtar and I came to Sayyiduna Ali (may Allah be pleased with him) on the day of al-Jamal. I said: Did the Prophet (peace and blessings be upon him) entrust you with any covenant other than the general one? He said: "No, only this," and he took out (a document) from the sheath of his sword, in which was written: "The blood of the believers is equal; the protection granted by the lowest of them is accepted, and they are one hand against those besides them. A believer is not to be killed in retaliation for a disbeliever, nor one under a covenant (dhimmi) while his covenant is in force."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16813
Sayyiduna Abdullah bin Abbas (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) said: "A slave is not to be given anything from the spoils of war, but he may be given from the leftover household goods, and his granting of protection is valid."
Umar bin Hafs al-Makki is da'if (weak).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16815
Fudayl bin Zayd (may Allah have mercy on him) said that he took part in seven military expeditions during the time of Sayyiduna Umar (may Allah be pleased with him). Then he mentioned a long hadith and said: When we returned, one of the slaves of the Muslims stayed behind, and he wrote a guarantee of protection for them on a sheet and threw it to them. The narrator said: We wrote to Sayyiduna Umar (may Allah be pleased with him) (about this matter), and the reply came from Sayyiduna Umar (may Allah be pleased with him): The slave of the Muslims is one of the Muslims; his protection is their protection. And he (may Allah be pleased with him) upheld his guarantee of protection.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16816