The addition of (and His forgiveness) in the greeting, and that its place is as a response to the greeting for one who began with a complete, full greeting.

The Shaykh : That this addition was not a known thing, and the people knew nothing about it, but they began to use it in a manner other than its proper one, and placed it in a place other than its proper place. This addition is only increased in one case, which is when the one greeting offers the complete greeting, and the complete greeting at the beginning ends with our saying: and His blessings. So the one greeting says: , so the one being greeted—in this state—has the choice; either to respond in kind or to respond with something better, . If he says: , he has responded in kind. If he adds , he has responded with something better. But the matter is not so when the one greeting says: , and the responder replies: . This addition here is not prescribed, because we added it in the first case:
First: to realize His saying—the Exalted—: . Second: to implement a hadith that I extracted in *Al-Sahihah* that the Prophet (peace and blessings be upon him) used to respond when they greeted—the second greeting—with the addition: .
And this hadith was criticized by some of our brothers. We are currently studying... that authentic reports have come that the limit of the greeting is , from Ibn 'Umar and Ibn 'Abbas and others. So if we begin the greeting, it is not permissible for us to add to . And if we respond, we add . This restriction is in the Qur'anic text and the Prophetic hadith. As for saying—for example—at the beginning: ; this is contrary to what the Salaf were upon. Therefore, or so, the response to the greeting is when the one greeting did not complete the greeting, and it remains on the original: , or if he said: , it is permissible for us to add to realize the better response. As for , that is a response to a complete, full beginning. This is a reminder, and the reminder benefits the believers.