Prayer: If Someone Says Only “Salām” to a Person Praying, Is Responding Obligatory?

Practical Laws of Islam as per the teachings of Imam Khamenei

Prayer: If Someone Says Only “Salām” to a Person Praying, Is Responding Obligatory?

English:

Question #513:

While greeting, someone says salām instead saying salāmun alaikum. If he greets a prying person like this, is it obligatory for the latter to answer his greeting?

Answer #513:

If people consider it as greeting and saying salām, it must be answered. However, in the praying person's answer, the word salām must, by caution, come first, like saying salāmun alaikum or as-salāmu alaikum. He should not answer by saying alaikumus-

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