Khalid (may Allah be pleased with him) and his brothers leaving their posts after the death of the Prophet (peace and blessings be upon him)

Khalid bin Sa'id bin Amr bin Sa'id narrates from his father (Sa'id bin Amr) that when news of the passing of the Messenger of Allah (peace and blessings be upon him) reached his uncles Khalid, Aban and Amr (the sons of Sa'id bin al-As), they left their posts and came back. Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) said to them: "No one is more entitled to these posts than the governors appointed by the Messenger of Allah (peace and blessings be upon him); go back to your duties." But they replied: "We will not serve as governors for anyone after the Messenger of Allah (peace and blessings be upon him)." So they set out for Syria for jihad, and all of them were martyred there.

It is narrated from Abu al-Yaqzan and others that Sayyiduna Khalid bin Sa'id bin al-As (may Allah be pleased with him) accepted Islam before Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him). (Imam al-Hakim says:) This is an error on the part of whoever said it, for I have already presented the narration that it was Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) who invited him to Islam, as a result of which he believed.

Muhammad bin Abdullah bin Abi Bakr narrates from his father that the Messenger of Allah (peace and blessings be upon him) had appointed Sayyiduna Khalid bin Sa'id (may Allah be pleased with him) as governor of Yemen. He arrived in Madinah after his (peace and blessings be upon him) passing and held back from giving the pledge of allegiance for two months, saying: "The Messenger of Allah (peace and blessings be upon him) appointed me as commander, and he (peace and blessings be upon him) did not dismiss me until Allah, the Mighty and Majestic, took his soul." He met Sayyiduna Ali bin Abi Talib and Sayyiduna Uthman bin Affan (may Allah be pleased with them both) and said: "O Banu Abd Manaf! Have you willingly given up your leadership, so that someone else now takes charge of it?" The narrator says: Sayyiduna Abu Bakr (may Allah be pleased with him) paid no attention to this remark of his, but it continued to rankle in the heart of Sayyiduna Umar (may Allah be pleased with him). Then, when Sayyiduna Abu Bakr (may Allah be pleased with him) sent the armies to Syria, the first person he appointed as commander over a quarter of the army was Khalid bin Sa'id. Sayyiduna Umar (may Allah be pleased with him) began saying: "Are you making him a commander, when what he did and said is before you?!" He kept on persuading Sayyiduna Abu Bakr (may Allah be pleased with him) until he dismissed Khalid and appointed Yazid bin Abi Sufyan as commander.
This hadith is sahih (authentic) on the condition of Imam Muslim, but the two Shaykhs did not record it.

Ahmad bin Sayyar relates that Sa'id, the father of Khalid bin Sa'id bin al-As, had twenty sons and twenty daughters. As for al-As bin Sa'id, the Commander of the Faithful Ali bin Abi Talib (may Allah be pleased with him) killed him as a polytheist on the day of Badr; and as for Khalid bin Sa'id, he was martyred at Marj al-Suffar in Muharram, 14 AH, during the caliphate of Sayyiduna Umar bin al-Khattab (may Allah be pleased with him).