It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that indeed the Messenger of Allah (peace and blessings be upon him) delivered a sermon on the day of the conquest of Makkah, and in it he also said this... and he narrated this hadith.
Hadith Referenceمسند الشهاب / 170
Hadith Gradingمحدثین:إسناده حسن
Hadith Takhrij«إسناده حسن ، وأخرجه أبو داود :2751، وابن ماجه : 2685 ، وأحمد : 2/ 193، 2/ 215»
Brief Explanation
Explanation: In Hadith number 135, Muslims were likened to a building, and in other narrations, they have been described as a single body (jism wahid). And now, in this hadith, they are being likened to a single hand. The meaning is that Muslims are united and in agreement against their enemy, just as the five fingers of a hand come together to form a fist, in the same way, Muslims too should all unite as one against their enemy.