How authentic is the story of Khalid ibn al-Walid drinking poison, what is the story behind it, and why did he drink it?

The story of Khalid ibn al-Walid drinking poison has been narrated in several sources. The gist of it is that when Khalid ibn al-Walid arrived in al-Hirah, some poison was brought to him. He placed it in his palm, uttered the name of Allah, and drank it, and it did not harm him. Ibn Taymiyyah mentioned that Khalid's drinking of poison was an indication of the truth of Islam and the veracity of the Messenger, and another time when he besieged a fortress and was asked to drink it. Therefore, if the story is authentic, his drinking of the poison was an act of trust in Allah and reliance upon Him, for the sake of supporting the religion, instilling fear in the disbelievers, and strengthening the faith of the Muslims. This might have been one of his karamat (miraculous acts) or due to a covenant he had with the Prophet, peace and blessings be upon him.