Be careful before making an oath; Respect your prophet; Follow your prophet even if you disagree with them; Take your oaths seriously.

In this hadith, Muhammad ibn al-Munkadir told that he saw Jabir ibn Abdullah swearing by Allah that Ibn as-Sa'id was the Dajjal or Antichrist. When he expressed his surprise at this oath, Jabir said he heard Umar swear to it in front of the Prophet Muhammad but the Prophet did not object. This hadith teaches us that we should be careful when making an oath and should not take it lightly because it is a serious matter in Islam. It also shows us how much respect and reverence Muslims have for their prophet and how they follow his example even when they are surprised or disagree with him.