Lean,
Why it is prohibited to take back one's gift? Apart from shameful? Haha! Abu Huraira (r.a) once reported: The Messenger of Allah (saw) said: Someone who takes back his gift is like a dog which eats until it is satisfied and then vomits what it has eaten and then swallows the vomit again.
Sounds terrible and disgusting, right? It is.
Cheers.
