From the Gulistan, II.31
A man, being tormented by a contrary wind in his belly and not having the power to retain it, unwittingly allowed it to escape. He said: 'Friends, I had no option in what I did, the fault of it is not to be ascribed to me and peace has resulted to my internal parts. Kindly excuse me.'Though the original seems to have an extra couplet at the end, which can be roughly translated as, "if you are visited by a sour-faced, uncongenial friend, don't try and prevent him from leaving."The belly is a prison of wind, O wise man.
No sage retains wind in captivity.
If wind twists thy belly let it out
Because wind in the belly is a burden to the heart.