Sayyiduna Husayl bin Kharijah al-Ashja'i (may Allah be pleased with him) narrates: I came to Madinah to sell some goods, and I was brought to the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) said: "I will give you twenty sa' of dates on condition that you guide my Companions to Khaybar." I did so. When the Prophet (peace and blessings be upon him) came to Khaybar and conquered it, I came, and the Prophet (peace and blessings be upon him) gave me the twenty sa'. Then I accepted Islam.
Al-Tabarani recorded it; its chain contains Abd al-Aziz bin Imran, who is da'if (weak).