Is it permissible to delay returning salaams because of enmity?

There is personal enmity between me and another person. If he greets me with salaam, is it permissible for me to respond after he has gone away, or do I have to return his salaam immediately?

Praise be to Allah, and blessings and peace be upon the Messenger of Allah:

The Hanafis and Shaafa’is are of the view that it is obligatory to return the salaams immediately.

Ibn ‘Aabideen said: delaying returning the salaam for no valid reason is makrooh tahreeman (very makrooh or disliked to the point of being almost haraam). The sin is not lifted by returning the salaam, but by repentance.