The point of divergence here rests upon two apparently contradictory ḥadīths.

The first is the narration of Anas, in which the Prophet—peace and blessings be upon him—said:

“Indeed the imām has only been appointed to be followed; so when he bows, bow; when he rises, rise; and when he says, ‘Samiʿa-llāhu liman ḥamidah,’ then say, ‘Rabbanā wa laka-l-ḥamd.’”

The second is the ḥadīth of Ibn ʿUmar which states that the Prophet—peace and blessings be upon him—
“Whenever he began the prayer he raised his hands level with his shoulders; and when he lifted his head from bowing, he raised them likewise and said, ‘Samiʿa-llāhu liman ḥamidah, Rabbanā wa laka-l-ḥamd.’”

Those who give precedence to the purport (mafhum) of Anas’s ḥadīth hold that the follower does not say “Samiʿa-llāhu liman ḥamidah,” nor does the imām say “Rabbanā wa laka-l-ḥamd.” Their proof is an argument from silence (dalīl al-khiṭāb): the ruling for what is left unspoken is taken to be contrary to what is explicitly stated.

Those who prefer Ibn ʿUmar’s report maintain that the imām does say “Rabbanā wa laka-l-ḥamd,” and that the congregant is obliged to follow him in saying “Samiʿa-llāhu liman ḥamidah,” by virtue of the general principle, “The imām was only appointed to be followed.” Others seek a reconciliation between the two reports by distinguishing between the imām and the follower.

The sound conclusion, however, is that Anas’s ḥadīth, by way of dalīl al-khiṭāb, implies that the imām does not say “Rabbanā wa laka-l-ḥamd” and the follower does not say “Samiʿa-llāhu liman ḥamidah.” Ibn ʿUmar’s narration, expressed explicitly, affirms that the imām does in fact say “Rabbanā wa laka-l-ḥamd,” and an explicit text is not to be set aside for an argument from silence, for the explicit is weightier.

Moreover, Anas’s report, in its general wording, requires that the follower pronounce “Samiʿa-llāhu liman ḥamidah” on the basis of the statement, “The imām was only appointed to be followed,” while the same report—by its argument from silence—indicates that he should not utter it. Hence a weighing must be made between generality and dalīl al-khiṭāb; and although general indications are ordinarily stronger, they themselves vary in strength, so that at times a particular argument from silence may surpass a weak general proof. By my life, the matter—so far as the congregant is concerned—is one of ijtihād.

As for the second issue—praying standing behind an imām who is seated—its upshot is that the scholars agree a healthy person may not perform an obligatory prayer seated when praying alone or leading others, in light of the divine command, “And stand before Allah in devout obedience” (al-Baqarah 2:238).

They differ, however, when the follower is healthy but the imām, due to illness, prays seated. Three opinions are reported:

1. The follower also prays seated. This is the view of Aḥmad, Isḥāq, and others.

2. The followers pray standing. Abū ʿUmar Ibn ʿAbd al-Barr states that this is the position of the majority of jurists across the regions: al-Shāfiʿī and his companions, Abū Ḥanīfah and his companions, the Ẓāhirīs, Abū Thawr, and others. According to them the congregation stands behind him even if the imām is unable to bow and prostrate, and merely gestures instead.