The ruling on greeting a busy person.

The Shaykh : Furthermore, it is not appropriate to offer the greeting to a person who is occupied in such a way that it would disturb him. If we see a person reciting the Qur'an to memorize it, and we are convinced or certain that greeting him would disturb him, the Sunnah is not to greet him, because it would occupy him. However, if we see him ready, looking at us, wanting us to greet him, then we should greet him, because leaving him without a greeting in that case would leave something in his heart. As for the one who is praying, the Companions (may Allah be pleased with them) used to greet the Prophet (peace and blessings be upon him) while he was praying, but the greeting was not returned with words; it was returned with a gesture, meaning, raise your hand like this so that it is clear to him that you have returned his greeting. Then, if he remains until he completes his prayer, return his greeting with words. If he has already finished, the gesture suffices. This is because the person praying is prohibited from speaking to humans, and what is prohibited by the Shari'ah is like what is physically deprived. Therefore, how does the mute person return the greeting? With a gesture, because he is deprived of speech and cannot speak. The person praying is also prohibited from speech, because it is not permissible for him to return the greeting, as that is speech to humans, and speech to humans in prayer is forbidden. But what do you say if a man greets us while we are praying, and we forget and return the greeting, saying "Peace be upon you"? Is his prayer invalidated? The answer is no, his prayer is not invalidated. Why? Because of the saying of Allah, Blessed and Exalted is He: This is general, and take this verse as a rule from Allah, Mighty and Majestic: every forbidden act that you do by mistake or forgetfulness is excused; you are not held accountable for it, it does not invalidate the act of worship, and no expiation is required for it, because the person is excused. Indeed, the excuse of ignorance has been reported regarding speech, and ignorance is the brother of forgetfulness. The excuse of ignorance in speech was reported in the story of Mu'awiyah ibn al-Hakam (may Allah be pleased with him). Mu'awiyah ibn al-Hakam entered with the Prophet (peace and blessings be upon him) while he was praying. A man from the people sneezed and said, "Praise be to Allah." Mu'awiyah ibn al-Hakam—Mu'awiyah ibn Abi Sufyan, Mu'awiyah ibn al-Hakam—said, "May Allah have mercy on you." The phrase "May Allah have mercy on you" is human speech that invalidates prayer. The people cast their eyes at him, meaning they looked at him with their eyes, disapproving of him. He said, "Woe to my mother," a phrase used for lamentation. They began hitting their thighs to silence him, and he became quiet. When he finished his prayer, the Prophet (peace and blessings be upon him) called him. Mu'awiyah said: "May my father and mother be his ransom, by Allah, he did not scold me or rebuke me, but he only said: , or as he said, and he did not order him to repeat the prayer. If speech in a state of ignorance had invalidated the prayer, he would have ordered him to do what? To repeat the prayer, just as he ordered the man who entered and prayed without settling in his prayer to repeat the prayer. In any case, we say: if you greet a person while he is praying and he forgets and returns it to you, his prayer is valid and not invalidated, because he was forgetful, and Allah the Exalted said: .