Umar used to swear by saying, "By my father," so the Prophet ﷺ forbade him, saying, "Whoever swears by anything other than Allah Most High has committed shirk." The other narrator said, "It is shirk."
حدثنا عبد الرزاق أخبرنا سفيان عن أبيه والأعمش ومنصور عن سعد بن عبيدة
كان عمر يحلف وأبي فنهاه النبي ﷺ قال من حلف بشيء دون الله تعالى فقد أشرك وقال الآخر وهو شرك
Its isnad is sahih. Saad bin Ubayda, his reliability was previously established at 620, and we add here that Bukhari mentioned him in al-Kabir 61/2/2, saying, "He heard from Ibn Umar." In H and K it appears as "Saeed bin Ubayda," which is an error we have corrected from M. The hadith previously appeared in the Musnad of Umar at 329, by way of Saeed bin Masruq, the father of Sufyan Thawri, from Saad bin Ubayda, from Ibn Umar, from Umar. It seems, as we said there, that Ibn Umar was present when his father took the oath. Sometimes he narrates it from Umar, and sometimes he narrates it directly without mentioning his father. See 4667 and 4703.Here in H it reads "he used to swear," and so on, which is an error. We have added the word "Umar" as a correction from K and M, since the one taking the oath was Umar, not his son Abdullah.In H it reads "wa huwa shirk," and in M it reads "huwa shirk," and we have adopted what is in K.