Sayyiduna Imran bin Husayn (may Allah be pleased with him) said: We used to count the false oath (al-yamin al-ghamus) among the major sins.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains Kathir Abu al-Fadl, from whom a group narrated, and no one declared him weak; the rest of its narrators are thiqat (trustworthy).