‘Umaarah bin Hazm (rahimahullah) narrates the following incident from Sayyiduna Ubayy bin Ka’b (radhiyallahu ‘anhu):
On one occasion, Rasulullah (sallallahu ‘alaihi wasallam) sent me to collect the zakaat that was due on the people’s wealth. While collecting zakaat from the people, I passed by a Sahaabi who also needed to discharge his zakaat. Accordingly, this Sahaabi gathered all his camels and presented them to me so that I could calculate the zakaat due on the camels. After examining the camels, I determined that his zakaat on the camels amounted to a single one-year old she-camel.
I thus said to him, “You need to discharge a single one-year old she-camel as this is the zakaat due on your camels.” Hearing this, the man replied, “A one-year old she camel neither gives milk, nor can it be used as a conveyance (hence, there is very little benefit in it). Instead of a one-year old she camel, here is a young, strong, large and fat she camel. Take this camel.” I replied, “I cannot take that which I was not instructed to take. However, Rasulullah (sallallahu ‘alaihi wasallam) is nearby. If you wish to go to him and present to him what you presented to me, you may do so. If Rasulullah (sallallahu ‘alaihi wasallam) accepts your offer (to give a better camel in zakaat), I will take the camel from you, but if he does not accept your offer, I will not take the camel.”