A vezier who had a stupid son gave him in charge of a scholar to instruct him and if possible to make him intelligent. Having been some time under instruction but ineffectually, the learned man sent one to his father with the words: ‘The boy is not becoming intelligent and has made a fool of me.’

When a nature is originally receptive
Instruction will take effect thereon.
No kind of polishing will improve iron
Whose essence is originally bad.
Wash a dog in the seven oceans,
He will be only dirtier when he gets wet.
If the ass of Jesus be taken to Mekkah
He will on his return still be an ass.