On the authority of Ibn Buḥaynah: that the Prophet (peace be upon him) prayed a prayer — I think it was the afternoon prayer — and when he was in the second [rakʿah], he stood up before sitting. Then, before he gave the salutation, he prostrated two prostrations.

1207 — Abū Bakr ibn Abī Shaybah narrated to us, Ibn Numayr, Ibn Fuḍayl, and Yazīd ibn Hārūn narrated to us (ḥ).
And ʿUthmān ibn Abī Shaybah narrated to us, Abū Khālid al-Aḥmar, Yazīd ibn Hārūn, and Abū Muʿāwiyah narrated to us; all of them from Yaḥyā ibn Saʿīd, from ʿAbd al-Raḥmān al-Aʿraj:
that Ibn Buḥaynah informed him: that the Prophet (peace be upon him) stood up after two [rakʿahs] of the noon prayer, having forgotten the sitting, until when he had finished his prayer except for the salutation, he prostrated the two prostrations of forgetfulness and gave the salutation.

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(1) Its chain of transmission is authentic. Al-Aʿraj: he is ʿAbd al-Raḥmān ibn Hurmuz, and Ibn Buḥaynah: he is ʿAbd Allāh ibn Mālik, and Buḥaynah is his mother.
It was also recorded by al-Bukhārī (829), (667), (1224), and (1230), Muslim (570), Abū Dāwūd (1034) and (1035), al-Tirmidhī (392), and al-Nasāʾī 3/19 and 34, via the path of al-Zuhrī, with this chain of transmission.
It is in the "Musnad Aḥmad" (22920) and "Ṣaḥīḥ Ibn Ḥibbān" (1938).

(2) The confirmed wording is from (S) and (M), and in (Dh): "until when he had finished his prayer and wanted to give the salutation, he prostrated…"

(3) Its chain of transmission is authentic. Ibn Numayr: he is ʿAbd Allāh, Ibn Fuḍayl: he is Muḥammad, Abū Khālid al-Aḥmar: he is Sulaymān ibn Ḥayyān, Abū Muʿāwiyah: he is Muḥammad ibn Khāzim al-Ḍarīr, and Yaḥyā ibn Saʿīd: he is al-Anṣārī.
It was also recorded by al-Bukhārī (1225), Muslim (575) (87), and al-Nasāʾī 2/244 and 3/20, via the path of Yaḥyā ibn Saʿīd, with this chain of transmission.
It was also recorded by al-Bukhārī (830) via the path of Jaʿfar ibn Rabīʿah, from al-Aʿraj, with it.
It is in the "Musnad Aḥmad" (22919).