The ruling on the greeting of the mosque, and do the two rak'ahs of the obligatory prayer suffice in place of the greeting of the mosque?

The questioner: Regarding this rule, if two obligatory duties coincide, we must perform this obligatory duty and that obligatory duty. O Shaykh, regarding the greeting of the mosque, on the view that it is obligatory, if he wants to pray Fajr.

The Shaykh: The same answer you heard.

The questioner: Does he pray twice?

The Shaykh: The same answer, but you distinguish between the greeting of the mosque and the Sunnah of Fajr.

The questioner: No, I mean the obligatory prayer.

The Shaykh : Yes?

The questioner : ... .

The Shaykh: The obligatory prayer?

The questioner: Yes, meaning, does the obligatory prayer suffice in place of the two rak'ahs of the greeting of the mosque?

The Shaykh: Ah, I thought the question was not in this form. We say in the hadith, as is not hidden from everyone - if Allah wills - the question I understood from the brother is: A man entered the mosque and the prayer was being performed, and he did not pray the greeting of the mosque; does the prayer of greeting drop by his entering the mosque and following the imam in the obligatory prayer; is that not so?

The questioner: Do we say on this rule that an obligatory duty does not suffice?

The Shaykh: Leave me alone with the rule, make the question clear to me?

The questioner: The question is that the obligatory duties, as we said ... .

The Shaykh: I understood, my brother, but what is the scenario?

The questioner: The scenario is if he did not pray Fajr, and entered a mosque, and started the obligatory prayer, and left the greeting of the mosque?

The Shaykh: That is the question - may Allah guide you - that is the question, what is the difference? The difference is that his scenario is that he entered the mosque and wants to follow the imam, you framed the question as him wanting to pray the obligatory prayer himself, "all roads lead to the mill". The question is: A man wants to pray the obligatory Fajr prayer in the mosque, and that is all we need; does he pray behind an imam or alone? So, if he prays the obligatory Fajr prayer, does the greeting of the mosque drop for him?
He suspectsThe questioner : that this issue, when I answer contrary to what comes to his mind, is a contradiction of what I said earlier, which is "that an obligatory duty does not suffice for another obligatory duty", so I will say in this scenario: The one who entered the obligatory Fajr prayer before praying the greeting of the mosque, the greeting of the mosque has dropped for him. Some listeners may suspect at that time that an obligatory duty has sufficed for another obligatory duty; we say this issue differs from what preceded. We want our brothers who find it difficult to bring a scenario other than this one in which they find an obligatory duty sufficing for another obligatory duty. As for this scenario; the Prophet (peace and blessings be upon him) said: , so the one who prayed the obligatory Fajr prayer, it is true of him that he did not sit except that he prayed two rak'ahs. Therefore, whoever holds that the greeting of the mosque is obligatory, and then says that this obligatory duty drops in this scenario; there is no contradiction in this scenario with the previous rule, which is: "that an obligatory duty does not suffice for another obligatory duty". Otherwise, we would say another scenario: A man vowed to fast a week - for example - or a day from every month, so the month of Ramadan arrived, and he intended his fasting for Ramadan along with his vowed day; does his fasting suffice for the two obligatory duties, the obligatory duty of Ramadan and the obligatory duty of the vow? This is a scenario. Another scenario, which is clearer: A man has days from the past Ramadan to make up, so he waits until the second Ramadan enters, and he intends and enters with one intention in another intention; who says that this suffices? It is necessary, and an obligatory duty does not suffice for another obligatory duty. The greeting of the mosque differs because it is linked to the cause of not sitting except after prayer, so the one who prayed the obligatory Fajr prayer, it is true of him that he sat after prayer.
Other than that?