The ruling on greeting those in the mosque

Question:
The sixth question is from the correspondent Mahmoud Sayyid Abu Zayd, who says: What is the ruling on one who greets those present in the mosque before performing the greeting of the mosque?

Answer:
This is the Sunnah: when one enters a congregation in the mosque, he greets them, even if they are praying. He says, "Peace be upon you." If he says, "And Allah's mercy and blessings," that is fine. The one in prayer responds with a gesture, like this, gesturing with his hand, a gesture to him. The one outside of prayer responds and says, "And upon you peace, and Allah's mercy and blessings." There is nothing wrong with this, and it is not disliked; rather, it is prescribed. The Companions used to greet the Prophet (peace and blessings be upon him) while he was praying, and he would respond to them with a gesture (peace and blessings be upon him).
As for the saying of some of the common people that one does not greet those in the mosque or the one who is praying, this is an error contrary to the Sunnah. Rather, one greets them and they respond to him, even if they are reciting. He says, "Peace be upon you," and when they hear the voice, they say, "And upon you peace." If he said, "And Allah's mercy," they say, "And upon you peace and Allah's mercy." They respond with the same as his words or more; because Allah said: [Al-Nisa: 86]. So if he says, "Peace be upon you," they say, "And upon you peace." If they add to it, "And Allah's mercy," it is better for them. If they add to it, "And His blessings," it is better for them.
As for if he says, "Peace be upon you, and Allah's mercy and blessings," then it is obligatory for them to say the same, so that they respond to his greeting, and they pause from recitation, then they resume recitation. And if they are in prayer, they respond with a gesture. Yes.