Allah's Messenger (ﷺ) met `Umar bin Al-Khattab while the latter was going with a group of camel-riders, and he was swearing by his father. The Prophet (ﷺ) said, "Lo! Allah forbids you to swear by your fathers, so whoever has to take an oath, he should swear by Allah or keep quiet."
Exposition of the Prohibition
This noble hadith from Sahih al-Bukhari (6646) establishes the fundamental Islamic ruling regarding oaths. The Messenger of Allah ﷺ encountered 'Umar ibn al-Khattab while he was traveling with companions, and heard him swearing by his father. The Prophet immediately corrected this practice, declaring it forbidden by Allah.
The wisdom behind this prohibition is manifold: Swearing by created beings implies attributing to them a status that belongs solely to Allah. It constitutes a form of shirk in worship, as oath-taking is an act of devotion that should be directed only to the Creator. Furthermore, swearing by fathers or other created beings diminishes the sanctity of Allah's name in the hearts of believers.
The Divine Alternative
The Prophet ﷺ provided the lawful alternative: "Whoever has to take an oath, he should swear by Allah or keep quiet." This instruction establishes two permissible paths: either swear by Allah's names and attributes, or remain silent if an oath is unnecessary.
Swearing by Allah acknowledges His absolute sovereignty and maintains the proper hierarchy of creation and Creator. The option of silence protects the Muslim from unnecessary oaths, which carry grave responsibility and potential expiation requirements if broken.
Scholarly Consensus and Application
The scholars of Islam are unanimous in prohibiting oaths by anything other than Allah. This includes swearing by the Prophet, parents, leaders, the Ka'bah, or any created being. Ibn Taymiyyah explains that such oaths constitute minor shirk if the swearer believes the sworn-by object has independent power, and major shirk if worship is directed to it.
The practical application requires Muslims to consciously reform their speech patterns. Common expressions like "I swear by my life" or "By the Prophet" must be replaced with "Wallahi" (By Allah) or similar permissible formulations. This hadith thus serves as both a corrective and an educational tool for purifying Islamic monotheism in everyday speech.