It is narrated from Sayyiduna Umar (may Allah be pleased with him) that once I was with the Prophet (peace and blessings be upon him) in a battle. On one occasion, I swore an oath, saying: «لا وابي» Then a man from behind said to me, "Do not swear by the names of your forefathers." I looked and saw that it was the Prophet (peace and blessings be upon him).
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 240
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف، رواية سماك عن عكرمة فيها اضطراب، خ: 6647، م: 1646