It is similar to if he had bowed and prostrated with him. Salih, Ibn Mansur, and others reported that he must begin the prayer anew as four rak'ahs. This is the apparent view of al-Khiraqi and Ibn Abi Musa, the choice of Abu Bakr, and the opinion of Qatadah, Ayyub al-Sakhtiyani, Yunus ibn 'Ubayd, al-Shafi'i, Abu Thawr, and Ibn al-Mundhir, because he did not catch a complete rak'ah, so he is not considered to have caught the Jumu'ah, just like the case before it.
Section: Whenever one who is crowded is able [to prostrate] on the back or foot of another person, he is required to do so, and it is sufficient for him. Ahmad said, in the narration of Ahmad ibn Hashim (10): He should prostrate on the back or foot of the man, and steady his forehead and nose, during the two Eids and Jumu'ah. This was also held by al-Thawri, Abu Hanifah, al-Shafi'i, Abu Thawr, and Ibn al-Mundhir. 'Ata', al-Zuhri, and Malik said: He should not do that. Malik said: The prayer is invalidated if he does, due to the Prophet's (peace and blessings of Allah be upon him) saying: "And steady your forehead on the ground" (11). Our evidence is what was narrated from 'Umar (may Allah be pleased with him) that he said: "If the crowding is intense, let him prostrate on his brother's back." This was recorded by Sa'id in his "Sunan" (12). He said this in the presence of the Companions and others on a day of Jumu'ah, and no dissenter appeared against him, so it constitutes consensus. Furthermore, because he has performed what he is able to do in a state of incapacity, it is therefore valid, like the sick person who prostrates on a pillow (13), and the report does not encompass the incapacitated, because Allah does not burden a soul beyond its capacity, nor does He order one who is incapable of something to perform it.
Section: If he is crowded during one of the two rak'ahs, it must be either in the first or
(9) In the original: "to prostrate". (10) Ahmad ibn Hashim ibn al-Hakam al-Antaki. Abu Bakr al-Khallal mentioned that he heard many hadiths from him in the year 270 or 271 AH, and he narrated excellent legal issues from Imam Ahmad. Tabaqat al-Hanabilah 1/82. (11) Its takhrij (authentication/source reference) was provided earlier in 2/122. (12) Recorded by 'Abd al-Razzaq, in: Chapter on one who attends Jumu'ah and is crowded such that he cannot bow with the Imam, from the Book of Jumu'ah. Al-Musannaf 3/233. (13) Al-Mirfaqah: the pillow.