It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) set out for Khaybar, he (peace and blessings be upon him) appointed Siba' bin Urfutah al-Ghifari (may Allah be pleased with him) as his deputy (in Madinah). When we arrived there, we attended the Fajr prayer with him. In the first rak'ah he recited Surah Maryam (Kaf Ha Ya 'Ayn Sad), and in the second, "Woe to those who give short measure" [Surah al-Mutaffifin: 1] . I said to myself: Woe to so-and-so, who has two measures; with one he takes in full (when receiving), and with the other he gives short (when giving). Then we went to Siba' bin Urfutah (may Allah be pleased with him) and he sent us off, and we reached the Messenger of Allah (peace and blessings be upon him) one day before or one day after the conquest of Khaybar.

Imam al-Hakim says: I heard Abu Abdullah Muhammad bin Ya'qub al-Hafiz say that Imam al-Shafi'i (may Allah have mercy on him) said: "If the hadith of Birwa' bint Washiq (may Allah be pleased with her) is proven authentic, I will adopt it as my position." Upon this Abu Abdullah said: Had I been in the presence of Imam al-Shafi'i (may Allah have mercy on him), I would have stood up and said: This hadith has indeed been proven authentic, so now adopt it as your position. Imam al-Hakim says: Imam al-Shafi'i (may Allah have mercy on him) was cautious because, although this narration is authentic, the fatwa in it belongs to Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), and the chain of the hadith is from a group of men of Ashja'; but our Shaykh Abu Abdullah (may Allah have mercy on him) ruled it authentic because a trustworthy narrator has explicitly named in it a Companion of the Messenger, Ma'qil bin Sinan al-Ashja'i (may Allah be pleased with him).