Is intentionally swearing by Allah a lie (al-yamin al-ghamūs) considered polytheism (shirk) with Allah?

The Divisive Oath (al-Yamin al-Ghamoos) is not polytheism (shirk), but it is one of the major sins (kaba'ir adh-dhunub) as mentioned in the Prophetic Hadith. One must hasten to sincere repentance for it. If a servant repents from it, Allah accepts his repentance, for Allah (the Most High) says: "And it is He who accepts repentance from His servants and pardons sins" (Quran 42:25), and He (the Most High) says: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins'" (Quran 39:53). Paying the expiation for the oath (kaffarat al-yamin) is more cautious.