It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Prophet sent me on an errand while going towards Banu Mustaliq. When I returned, the Prophet (peace and blessings be upon him) was praying facing east on his camel. I wanted to speak, but the Prophet (peace and blessings be upon him) gestured with his hand. This happened twice. Then I heard the Prophet (peace and blessings be upon him) reciting, and he was gesturing with his head. After finishing the prayer, the Prophet (peace and blessings be upon him) said: What happened regarding the task I sent you for? I did not reply because I was praying.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 15175