The prohibition of taking the best of wealth in zakah and of transgressing in charity

It is narrated from Sayyiduna Umar (may Allah be pleased with him) that some of the zakah goats were driven past him, among them a goat with a large udder. On (seeing) it, he (may Allah be pleased with him) said: "I think its owners did not give this goat willingly. Do not take the choicest and most valuable portions of the Muslims' wealth (as zakah), do not put people to trial, and keep away from the special animals that give milk or are raised for food."

It is narrated from Sayyiduna al-Sunabih al-Ahmasi (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) saw an exceptionally beautiful and fine she-camel among the camels of zakah and sadaqah, and said (in astonishment and warning): "May Allah destroy him (that is, why did he take such fine property from the zakah wealth?)" At this (the zakah collector) said: "O Messenger of Allah! I exchanged two ordinary, small camels of the herd for this one she-camel." On hearing this, he (peace and blessings be upon him) said: "Then this exchange is fine."
Imam Abu Ya'la has narrated this hadith with his chain from Abu Bakr.

According to the narration of Imam Abu Ya'la (may Allah have mercy on him), an elder of the tribe of Banu Tamim relates: In the time of the rule of al-Hajjaj bin Yusuf al-Thaqafi, he came and sat with me in the mosque of Basrah. In his hand were a staff and a written document which he was holding. He asked me: "O servant of Allah! Do you think this writing will be of any use to me with this master of yours (the ruler of the time)?" I asked: "What kind of writing is this?" He replied: "It is the decree that the Messenger of Allah (peace and blessings be upon him) had written for us." I asked: "How did you obtain it?" He told me that he came to Madinah with his father. Then he mentioned the whole incident: that his father asked (Sayyiduna Talhah (may Allah be pleased with him)) to have a document written for us by the Messenger of Allah (peace and blessings be upon him) stating that no injustice would be done to us in the collection of our sadaqah. Sayyiduna Talhah (may Allah be pleased with him) said: "This justice is the right of every Muslim." We said: "Even if it is so (we still want a written guarantee)." So he took us with him to the Prophet (peace and blessings be upon him) and said: "O Messenger of Allah! These two wish that you write for them that no injustice be done to them in the matter of their sadaqah." He (peace and blessings be upon him) said: "This is the right of every Muslim." He said again: "O Messenger of Allah! It is their heartfelt wish that they have a document from you." So he (peace and blessings be upon him) had this decree written for us. Now (the elder said): "Do you think this writing will benefit me with this master of yours? By Allah! Great injustice and wrong is being done to us in the matter of our sadaqah." I (the narrator) replied: "By Allah! Then I do not think at all that it will be of any use before him (the oppressor)."