Two men saw a slave walking through a street with a fetter on one of his feet. One of the men said :
“The weight of the fetter on the foot of the slave is so much and if it was not my wife stands divorced.”
The other man suggested that the weight of the fetter was different one and he also made a bet that if the weight thereof was that which was suggested by his companion his wife would stand divorced.
Agreeing to the bet they both went to the master of the slave and requested him to take out the chain from the foot of his slave so that it could be weighed. They also mentioned
to him the bet they had made.
The master of the slaves when heard of the bet he told the two men that he had taken an oath that the fetter would be removed from the foot of the slave after completion of a certain period of time and that if he removed it before the expiry of that period of time his wife would also stand divorced. Therefore, he said, he could not remove the fetter from the foot of his slave before the expiry of that period of time.
When the case was taken to HazratOmar (RA) he ordered the two men who had made the bet to divorce their wives, because he could not order the master of slave to remove the fetter from the foot of his slave before the expiry of the period of time in question under any rule or practice of human society or under any clause of the religious law.
When Hazrat Ali (A) heard of this decision of Hazrat Omar (RA) in the case in question by the two men who had gone to him with an appeal, he said to them that it was quite easy to take the weight of the fetter without removing it from the foot of the slave.
He then sent for a big pot open on all sides and deep enough to contain sufficient water for drowning the foot and the fetter of the slave therein.
When the slave put his foot with the fetter thereon in the pot containing the fixed quantity of water, the water rose to a certain point in the pot which was marked.
When the fetter of the slave was raised towards the knee of the slave with the help of thread tied to it, the level of water fell down to a certain point in the pot, which was also duly marked under the orders of Hazrat Ali (A).
Then he ordered for putting iron dust in the pot slowly and gradually so that the water could rise to the first mark. There after, he ordered the slave to take out his foot from the pot to let the water fall down to its original level in the pot where after he ordered the weighing of the iron-dust saying that that was the weight of the fetter. (Tehzibul Ahkam; Biharul Anwar, vol. 9, p. 465).