What the follower says when rising from Rukū’

بسم الله الرحمن الرحيم

Abū Hurayrah narrated from the Messenger (ﷺ):

إذا قال الإمام: سمع الله لمن حمده، فقولوا : اللهم ربنا لك الحمد، فإنه من وافق قوله قول الملائكة غفر له ما تقدم من ذنبه

“When the Imām says Sami’a Allāhu liman hamidah, say Allāhumma Rabbanā Lakal-Hamd, for if ones saying synchronises with the saying of the angels he will be forgiven for his past sins.” (Abū Dawūd 848. Declared Sahīh by Al-Albānī)

Imām al-Sha’bī said: “The people behind the imām do not say “Sami’a Allāhu liman hamidah”, but rather they should say “Allāhumma rabbanā lakal-hamd” (Abū Dawūd 849, Ibn Abī Shaybah 2598 – Sahīh)

This has also been authentically narrated from the statement of Ibn Mas’ūd and Abū Hurayrah, and from the action of Ibn ‘Umar:

Ibn Mas’ūd (رضي الله عنه), who said: “When the imām says “Sami’a Allāhu liman hamidah,” the one behind him says “Allāhumma rabbanā lakal-hamd.” (Ibn Abī Shaybah 2597 and others)

Abū Hurayrah (رضي الله عنه)  said: “When the imām raises his head from rukū’ and says “Sami’a Allāhu liman hamidah,” then say “Rabbanā lakal-hamd.” (al-Awsat 1421 and others)

Nāfi’ narrated that Ibn ‘Umar (رضي الله عنه)  used to say when he was a follower: when the imām said “Sami’a Allāhu liman hamidah,” Ibn ‘Umar said “Allāhumma rabbanā lakal-hamd.” (al-Awsat 1420)

Nothing contrary to this has been authentically narrated from any of the Companions.

Ibn al-Mundhir said in al-Awsat (3/162): “It is firmly established (thābit) from the Prophet (ﷺ) that he said: ‘And when the imām says “Sami’a Allāhu liman hamidah,” then say “Rabbanā lakal-hamd.”‘ So restricting oneself to what the Prophet (ﷺ) taught the follower to say is more beloved to me.”

Ibn Rajab said in al-Fath 5/74: “Those who said used this as evidence that the ma’mūm (one being led in prayer) does not say “sami’a Allāhu liman hamidah” (Allāh hears the one who praises Him) like the imām (prayer leader), and it is the saying of Mālik, al-Thawrī, al-Awzā’ī, Abū Hanīfah, and Ahmad, and it was narrated from Ibn Mas’ūd, Abū Hurayrah, and al-Sha’bī.

(Above taken from Fadl al-Rahīm al-Wadūd, Takhrīj Sunan Abī Dāwūd 9/366-367)