On the authority of ʿAbdullah ibn ʿAmr, who said: I was told that the Messenger of Allah, peace and blessings be upon him, said: "A man's prayer sitting is half of the prayer." So I came to him and found him praying sitting, and I placed my hand on my head. He said: "What is the matter with you, O ʿAbdullah ibn ʿAmr?" I said: I was told, O Messenger of Allah, that you said: "A man's prayer sitting is half of the prayer," and you are praying sitting. He said: "Indeed, but I am not like any one of you."(1)

951 - Musaddad narrated to us, Yaḥyā narrated to us, on the authority of Ḥusayn al-Muʿallim, on the authority of ʿAbdullah ibn Buraydah, on the authority of ʿImrān ibn Ḥuṣayn: that he asked the Prophet, peace and blessings be upon him, about a man's prayer sitting, and he said: "His prayer standing is better than his prayer sitting, and his prayer sitting is half of his prayer standing, and his prayer lying down is half of his prayer sitting."(2)

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(1) Its chain of transmission is authentic. Jarīr: he is Ibn ʿAbd al-Ḥamīd al-Ḍabbī, and Manṣūr: he is Ibn al-Muʿtamir, and Abū Yaḥyā: he is Muṣdaʿ al-Aʿraj.
Muslim (735) and al-Nasāʾī in al-Kubrā (1365) also narrated it via multiple paths from Manṣūr, with this chain of transmission.
It is in Musnad Aḥmad (6512).
It was also narrated in abbreviated form with the wording: "The prayer of one sitting is half of the prayer of one standing" by Ibn Mājah (1229) via the path of Ḥabīb ibn Abī Thābit, from ʿAbdullah ibn Bābāh, from ʿAbdullah ibn ʿAmr.
There is disagreement regarding its chain of transmission from Ḥabīb ibn Abī Thābit, as we have clarified in our commentary on Sunan Ibn Mājah. Al-Nasāʾī also narrated it in al-Kubrā (1376) via the path of al-Zuhrī, from ʿĪsā ibn Ṭalḥah, from ʿAbdullah ibn ʿAmr, raised to the Prophet. He said: This is an error, and the correct version is al-Zuhrī from ʿAbdullah ibn ʿAmr as a suspended narration (mursal). We say: Mālik narrated it in 1/136 from al-Zuhrī from ʿAbdullah ibn ʿAmr.

(2) Its chain of transmission is authentic. Yaḥyā: he is Ibn Saʿīd al-Qaṭṭān, and Ḥusayn al-Muʿallim: he is Ibn Dhakwān.
Al-Bukhārī (1115) and (1116), al-Tirmidhī (371), al-Nasāʾī in al-Kubrā (1366), and Ibn Mājah (1231) also narrated it via multiple paths from Ḥusayn al-Muʿallim, with this chain of transmission.
It is in Musnad Aḥmad (19887) and Ṣaḥīḥ Ibn Ḥibbān (2513).
See what follows it.