Sayyiduna Wahshi bin Harb (may Allah be pleased with him) said: Sayyiduna Abu Bakr (may Allah be pleased with him) appointed Sayyiduna Khalid bin al-Walid (may Allah be pleased with him) as commander to fight the apostates, and said: I heard the Prophet (peace and blessings be upon him) say: "The best servant of Allah, and the best member of his clan, is Khalid bin al-Walid, one of the swords of Allah, whom Allah Almighty has drawn from its sheath against the disbelievers and the hypocrites."
Imam Ahmad recorded this report, and Imam al-Tabarani recorded something similar, and the narrators of both reports are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15875
Hadith Gradingمحدثین:إسنادہ صحیح
Hadith Takhrij«اخرجه الطبراني فى المعجم الكبير (3798) اخرجه احمد فى المسند (43) ، أخرجه مسند أحمد برقم: 44، وأخرجه المستدرك على الصحيحين برقم: 5346»