Another possible meaning is the transmission of knowledge: the Companions learned from him—peace and blessings be upon him—then the Successors learned from the Companions, and so on down the generations.

6 – The well-known view in Imām Aḥmad’s school, as cited by the author of Sharḥ al-ʿUmda, is that a follower’s prayer behind an imam is valid in any mosque, whether or not the follower sees the imam or those standing behind him. The mosque is, by definition, a place prepared for people to gather for congregational prayer. Likewise, a follower praying outside the mosque may validly follow the imam if he can see the imam himself or some of the worshippers. The prayer is invalid, however, if a roadway or a flowing river separates the imam and the follower, even if the takbīr can be heard.

7 – Shaykh al-Islām said: “The congregational prayer (ṣalāt al-jamāʿah) is so named because the worshippers actually come together in one place and at one time. If they forgo that, the act becomes impermissible by unanimous agreement of the leading jurists.”

8 – Based on this statement and the consensus it records, it is clear that joining a prayer via radio or television is invalid when the person following is physically remote from the congregation, because he is not with them in the place of assembly.

9 – Shaykh ʿAbd al-Raḥmān al-Saʿdī said: “The correct ruling is that whenever a follower can keep track of the imam’s movements by sight or by sound, his following is valid—whether he is inside the mosque or outside it, even if a road separates them—because there is no evidence for declaring it invalid.” Imām al-Nawawī, however, stated that for the prayer to be valid the follower must know the imam’s transitions, whether the prayer is inside a mosque or elsewhere; such knowledge is obtained by hearing the imam directly, by hearing those behind him, or by relying on either of these means. Al-Nawawī—may Allah have mercy on him—further stipulated that when the prayer is outside a mosque the distance must not be excessive, and this is the position of the majority of scholars.

Scholarly disagreement
The jurists differ over the point at which it is recommended to stand for the opening of the prayer.