What is the authenticity of the story of Lady Khadijah uncovering her hair to verify the angelic nature of Gabriel (peace be upon him), as mentioned in "Sirat Ibn Hisham"?

This hadith is weak in its chain of transmission due to interruption, as Isma'il ibn Abi Hakim did not meet Sayyidah Khadijah. Some Christians have exploited the weakness of this hadith to attack the prophethood, claiming that the Prophet did not recognize the revelation and asked Khadijah to verify it. However, even if the hadith were authentic, Al-Bayhaqi responded by stating that Khadijah was seeking assurance as a precaution for her faith, while the Prophet was certain of what came to him from Jibril. He also mentioned that the narration does not imply the Prophet's lack of knowledge of the revelation; rather, it was Khadijah who asked for verification.