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:6022 – Abū ʿAmr al-Adīb > Abū Bakr al-Ismāʿīlī > al-Haytham b. Khalaf al-Dūrī > Saʿīd b. Yaḥyá al-Umawī from my father > Ibn Jurayj > Mūsá b. ʿUqbah > Nāfiʿ > Ibn ʿUmar Naḥw from Qawl Mujāhid Idhā Ākhtalaṭūā Faʾinnamā > al-Dhikr And ʾIshārah Bi-al-Rraʾs Wazād Ibn ʿUmar

[Machine] About the Prophet ﷺ : "Even if they are more than that, let them pray standing and riding."  

البيهقي:٦٠٢٢ – وَأَخْبَرَنَا أَبُو عَمْرٍو الْأَدِيبُ ثنا أَبُو بَكْرٍ الْإِسْمَاعِيلِيُّ أَخْبَرَنِي الْهَيْثَمُ بْنُ خَلَفٍ الدُّورِيُّ ثنا سَعِيدُ بْنُ يَحْيَى الْأُمَوِيُّ ثنا أَبِي ثنا ابْنُ جُرَيْجٍ عَنْ مُوسَى بْنِ عُقْبَةَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ نَحْوًا مِنْ قَوْلِ مُجَاهِدٍ إِذَا اخْتَلَطُوا فَإِنَّمَا هُوَ الذِّكْرُ وَإِشَارَةٌ بِالرَّأْسِ وَزَادَ ابْنُ عُمَرَ

عَنِ النَّبِيِّ ﷺ وَإِنْ كَانُوا أَكْثَرَ مِنْ ذَلِكَ فَلْيُصَلُّوا قِيَامًا وَرُكْبَانًا  

رَوَاهُ الْبُخَارِيُّ فِي الصَّحِيحِ عَنْ سَعِيدِ بْنِ يَحْيَى بْنِ سَعِيدٍ

See similar narrations below:

Collected by Bukhārī
bukhari:943 – Saʿīd b. Yaḥyá b. Saʿīd al-Qurashī from my father > Ibn Jurayj > Mūsá b. ʿUqbah > Nāfiʿ > Ibn ʿUmar Naḥw from Qawl Mujāhid Idhā Ākhtalaṭūā Qiyām And Zād Ibn ʿUmar

Ibn ʿUmar said something similar to Mujahid's saying: Whenever (Muslims and non-Muslims) stand face to face in battle, the Muslims can pray while standing. Ibn ʿUmar added, "The Prophet ﷺ said, 'If the number of the enemy is greater than the Muslims, they can pray while standing or riding (individually).' "  

البخاري:٩٤٣ – حَدَّثَنَا سَعِيدُ بْنُ يَحْيَى بْنِ سَعِيدٍ الْقُرَشِيُّ قَالَ حَدَّثَنِي أَبِي قَالَ حَدَّثَنَا ابْنُ جُرَيْجٍ عَنْ مُوسَى بْنِ عُقْبَةَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ نَحْوًا مِنْ قَوْلِ مُجَاهِدٍ إِذَا اخْتَلَطُوا قِيَامًا وَزَادَ ابْنُ عُمَرَ

عَنِ النَّبِيِّ ﷺ وَإِنْ كَانُوا أَكْثَرَ مِنْ ذَلِكَ فَلْيُصَلُّوا قِيَامًا وَرُكْبَانًا