It is narrated from Sayyiduna Samurah bin Jundub (may Allah be pleased with him); he said: When we were alarmed, the Messenger of Allah (peace and blessings be upon him) would command (us to keep to) unity, patience and calm, and when we fought, he would also command the same.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 7072