Sayyiduna Amr bin Ya'la (may Allah be pleased with him) narrated: I was present at the time of an obligatory prayer while we were riding our mounts with the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) led us in prayer: he went ahead of us, he led us, and we prayed on our mounts.
Imam al-Bazzar recorded it; its chain contains a narrator, Abd al-A'la bin Amir, and he is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2981