Prayer: If I Missed Responding to Salām Immediately, Is It Still Obligatory to Reply?

Practical Laws of Islam as per the teachings of Imam Khamenei

Prayer: If I Missed Responding to Salām Immediately, Is It Still Obligatory to Reply?

English:

Question #510:

A person was greeted with the salām but did not reply due to inattention or some other reason so that a short span of time passed, is it still obligatory for him to respond to it?

Answer #510:

If the delay is of such a length that a reply is no longer considered a reply (to the greeting), then it is not obligatory.

-Imam Khamenei, Practical Laws of Islam, Importance and Conditions of Prayer