Grading: All its narrators are thiqah, but there is disagreement over 'Asim bin Muhammad in its chain.
Technical note / Defect ('illah): Abu Damrah (whose name is Anas bin 'Iyad bin Damrah) narrated it from 'Asim bin Muhammad and attributed it to 'Abd Allah bin 'Umar (may Allah be pleased with them both), and we did not find this route anywhere other than with the author (al-Hakim). Whereas Abu Mu'awiyah al-Darir and Ahmad bin Yunus narrated it from 'Asim bin Muhammad and attributed it to 'Umar bin al-Khattab (may Allah be pleased with him). Imam al-Bukhari says that the narration of 'Umar is more likely to be correct, as mursal (with a break in the chain).

Reference / Source: Ibn Abi Shaybah (12756, ed. Muhammad 'Awwamah) narrated it from Abu Mu'awiyah Muhammad bin Khazim, and Imam al-Bukhari in "al-Tarikh al-Kabir" (2/129), and through him Imam al-Bayhaqi (15/31), via Ahmad bin Yunus.
Details of the narration: Both these narrators narrate it from 'Asim bin Muhammad bin Zayd, who said: I heard my father say that 'Umar bin al-Khattab (may Allah be pleased with him) said: "An oath is either a sin or a cause of regret." Imam al-Bukhari said that this narration of 'Umar (may Allah be pleased with him) is more likely to be correct, as mursal.
Technical note / Defect ('illah): We say: the narrators of this chain are thiqah, but there is a break (inqita') in it, because Muhammad bin Zayd did not live in the time of 'Umar bin al-Khattab (may Allah be pleased with him) (i.e. meeting him is not established).