Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) narrates: Once I intended to go to Khaybar. I presented myself before the Prophet (peace and blessings be upon him) while he was in the mosque. I greeted him with salam, then I said: "I wish to go to Khaybar, so I wanted to greet you, and let this salam be my last act in Madinah. May my parents be sacrificed for you!" Sayyiduna Jabir (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said to me: "When you go to my agent in Khaybar, take fifteen wasqs from him." Sayyiduna Jabir (may Allah be pleased with him) says: When I turned to leave, he called me back and said: "Take thirty wasqs from him. By Allah! For the family of Muhammad in Khaybar, there are only those dates. If he asks you for any sign (i.e., proof), then place your hand on his collarbone." After this, he mentioned the entire hadith. A solitary report (khabar wahid) makes action obligatory.