Chayai Sarah
The passuk says ויפתח הגמלים. What is the meaning of ויפתח? Rashi explains that Eliezer undid the muzzles of the camels. He had closed their mouths so they wouldn’t pasture on other peoples fields. Earlier the passuk says “the servant took ten camels from the camels of his master.” Why is there an emphasis on “the camels of his master”? Rashi explains they were recognizable from other camels. Avraham’s camels were muzzled so they wouldn’t eat from other people’s fields, whereas others weren’t.
The Ramban brings: Rav Huna and Rav Yirmiya asked Rav Chiya beRebbe Abba “were the camels of Avraham not similar to the donkey of Rabi Pinchas ben Yair?” Once Rabi Pinchas’s donkey was stolen and they held it for three days and it didn’t eat. They said it will end up dying and smelling up the cave which we are living in. They returned it to its owner. Once it entered it neighed like any other donkey because it wanted to eat. When the robbers fed tevel or even safek tevel it wouldn’t eat. Only after separating proper terumos and ma’asros did it eat.
It is impossible that Rabi Pinchas’s chasidus would be greater than Avraham’s. If Rabi Pinchas’s donkey refrained from eating things which were assur to its owner then certainly Avraham’s camels didn’t need to be muzzled.
Therefore the Ramban explains ויפתח means that he opened the ropes which grouped the camels together or undid the ropes which held the seat on the camel.
The Sifsei Chachamim answers for Rashi that out of Eliezer’s chasidus he muzzled them so they wouldn’t even eat things which were permissible, like from the sides of public property which people are mafkir. The Re’eim says there is a rule of אין סומכין על הנס or where damage is easily found one has to be careful.
The Maharziv answers that Avraham’s camel which he rode on was definitely like Rabi Pinchas’s donkey, while the rest needed to be muzzled!
I heard from R’ Tzvi Merzel that really Avraham didn’t need to muzzle his animals but it was to teach other people to not take what is not theirs and to care for others’ property!