Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
bayhaqi:2578 – Abū Zakariyyā b. Abū Isḥāq al-Muzakkī > Aḥmad b. Salmān al-Faqīh > al-Ḥasan b. Mukram > ʿAlī b. ʿĀṣim > Khālid al-Ḥadhhāʾ > ʿAlī b. al-Aqmar > Abū al-Aḥwaṣ > ʿAbdullāh / Ibn Masʿūd

[Machine] Whoever does not catch up with the imam while he is bowing, did not catch that unit (of prayer).  

البيهقي:٢٥٧٨ – أَخْبَرَنَا أَبُو زَكَرِيَّا بْنُ أَبِي إِسْحَاقَ الْمُزَكِّي أنبأ أَحْمَدُ بْنُ سَلْمَانَ الْفَقِيهُ أنبأ الْحَسَنُ بْنُ مُكْرَمٍ ثنا عَلِيُّ بْنُ عَاصِمٍ ثنا خَالِدٌ الْحَذَّاءُ عَنْ عَلِيِّ بْنِ الْأَقْمَرِ عَنْ أَبِي الْأَحْوَصِ عَنْ عَبْدِ اللهِ يَعْنِي ابْنَ مَسْعُودٍ قَالَ

مَنْ لَمْ يُدْرِكِ الْإِمَامَ رَاكِعًا لَمْ يُدْرِكْ تِلْكَ الرَّكْعَةَ  

See similar narrations below:

Collected by Suyūṭī