I needed the reference of a hadith to complete this answer.
Many of us have heard of a well-known hadith where the tahajjud salah of our beloved Prophet PBUH was described by a sahaba, where he recited nearly 5 juz before going for rukoo.
I cannot remember the name of that Sahaba R. and the exact hadith. I needed the reference of that hadith.
I presume you are referring to the companion Hudhayfah ibn Al-Yaman, who narrated this hadith in Sahih Muslim:
عن أبي عبد الله حذيفة بن اليمان رضي الله عنهما قال: صليت مع النبي صلى الله عليه وسلم ذات ليلة فافتتح البقرة فقلت يركع عند المائة ثم مضى. فقلت يصلي بها في ركعة، فمضى. فقلت يركع بها، ثم افتتح النساء. فقرأها ثم افتتح آل عمران فقرأها يقرأ مترسلاً إذا مر بآية فيها تسبيح سبح وإذا مر بسؤال سأل وإذا مر بتعوذ تعوذ. ثم ركع فجعل يقول: سبحان ربي العظيم. فكان ركوعه نحواً من قيامه ثم قال: سمع الله لمن حمده، ربنا لك الحمد. ثم قام قياماً طويلاً قريباً مما ركع ثم سجد فقال: "سبحان ربي الأعلى" فكان سجوده قريباً من قيامه
Hudhaifah (May Allah be pleased with him) reported: I offered Salat (Tahajjud - optional night prayer) with the Prophet (ﷺ) one night, and he started reciting (Surat) Al-Baqarah. I thought that he would bow at the end of one hundred Verses, but he continued reciting; I, then, thought that he would perhaps recite the whole (Surah) in a Rak'ah, but he proceeded on, and I thought he would perhaps bow on completing (this Surah); he then started (reciting Surat) An-Nisa'; he then started (Surat) Al-'Imran and his recitation was unhurried. And when he recited the Verses which referred to the Glory of Allah, he glorified Him (by saying Subhan Allah - My Rubb, the Supreme is far removed from every imperfection), the Great, and when he recited the Verses that mention supplication, he supplicated, and when he recited the Verses that mention seeking Refuge of the Rubb, he sought (His) Refuge. Then he bowed and said: "My Rubb, the Supreme is far removed from every imperfection (Subhana Rabbiyal-Azim);" his bowing lasted about the same length of time as his standing (and then on returning to the standing posture after Ruku') he said: "Allah listened to him who praised Him (Sami' Allahu liman hamidah, Rabbana wa lakal hamd)." Then he stood about the same length of time as he had spent in bowing. He then prostrated himself and said: "My Rubb, the Supreme is far removed from every imperfection (Subhana Rabbiyal-A'la)," and his prostration lasted nearly the same length of time as his standing.
The link above does not mention the full chain, but it was narrated through multiple chains that go through:
