Is it permissible to greet those who are currently performing Salat (prayer)?

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It is permissible to offer the greeting (salam) to a group of people who are engaged in prayer. Imam Ahmad permits this, and Ibn al-Mundhir narrated this ruling from him. Ibn Umar also performed this action. Those who permit it argue based on the verse: {But when you enter houses, greet yourselves with a greeting from Allah - blessed and good} (Quran 24:61), meaning greet your co-religionists. They also cite the action of the Prophet (peace be upon him), who responded to the greeting of his companions with a gesture while praying, without disapproving of their initial greeting.