[ Ruling on being led in prayer by one who is not the most entitled 1]

Answer: The ḥadīth is phrased as information but means a command. However, necessity and excuses have their rulings, as indicated by His saying, “… except for that to which you are compelled.” [al-Anʿām:119] and His saying, “… except if you fear from them a threat (taqiyyah).” [Āl ʿImrān:28], among many other texts.
Accordingly, if there is an excuse, there is no harm in departing from what the ḥadīth entails. If there is no excuse, what appears to me is that the prayer does not become invalid; what is invalidated in this case is the virtue of congregation, not the essence of the prayer.
The proof is that the ḥadīth came to clarify who is worthy to lead the people, and that if they put him forward they attain the virtue of congregational prayer and its multiplied reward. If the Muslims comply with this guidance of their Prophet—may Allah bless him and his family and grant them peace—by putting forward the worthiest, they obtain the multiplied reward; whereas if they do not adhere to that guidance but contravene it, they miss the virtue of congregation and its multiplied rewards.
As for the permission of the one most entitled to another to advance to lead: if it is for an excuse, there is no problem—such as putting forward the father, the uncle, the shaykhs of knowledge, or putting forward an elder brother or an elder among the righteous. There are clear excuses of this kind; for if the worthiest did not put such people forward, he would be accused of ill manners, would open the door to people’s talk against him, and the ignorant would find an opening to attack his honor and harm him.
But if the most entitled puts another forward without excuse, we ought first to clarify whether his precedence and his right to be put forward is a right belonging to him, or a right belonging to others.
What appears is that precedence is the right of the imām, due to His saying, “We made from among them leaders guiding by Our command when they were patient.” [as-Sajdah:24] In this verse Allah clarifies that He granted them leadership as a reward for their patience; thus, leadership is their right: if they wish, they take it; and if they wish, they leave it.
Moreover, Imām al-Hādī Yaḥyā b. al-Ḥusayn—blessings of Allah be upon him—put his uncle Muḥammad b. al-Qāsim—peace be upon them—forward to lead the prayer, and likewise did others.
I have seen in our own time many scholars put others forward without any apparent excuse.
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1