Fulfil a promise made. Do not act in conflict with a promise without any valid reason.
Do not make promises in haste.
Do not make promises pertaining to unlawful things. It is not permissible to fulfil such unlawful promises.
Do not make a promise if you have no intention of fulfilling it.
If a
child is enticed with something, it will also be a promise which should be honoured.
Abdullah Ibne Aamir
radhiyallahu anhu 
narrates that one day (while he was a
child), his mother called him saying that she had
something to give to me. Rasoolullaah
sallallahu alayhi
wasallam 
who happened to be present, asked: "What do you intend giving him?" Aamir's radhiyallahu anhu
mother replied: "I intend to give him some dates." Rasoolullaah
sallallahu alayhi wasallam
commented:
"Verily,
if you do not give him anything, a lie will be recorded against you."