The obligation of العمرة is one of the well-known points of scholarly difference among the four schools of Sunni Islamic jurisprudence, and both positions are supported by legitimate evidence. The Shafi'i and Hanbali schools hold that العمرة is واجب (فرض or واجب) once in a lifetime for every Muslim who meets the conditions of ability, similar to الحج. Their primary evidence is القرآنic verse: 'And complete the الحج and العمرة for Allah' (2:196), which they interpret as a command to perform both الحج and العمرة. They also cite the hadith in which النبي was asked about العمرة: 'Is it واجب?' and he replied, 'No, but if you perform العمرة it is better for you,' though the Shafi'i scholars note some chains of this narration are weak, and they rely on stronger evidence for the obligation.
The Hanafi and Maliki schools hold that العمرة is a strongly مستحب السنة (سنة mu'akkadah) but not واجب. Imam Abu Hanifah and Imam Malik both interpreted القرآنic verse 'Complete the الحج and العمرة for Allah' as referring to completing the rites once you have begun them (i.e., if you start الحج or العمرة, you must finish them), rather than as a command to initiate both. They also cite the hadith of Jabir in which النبي was asked whether العمرة is واجب and he said it is not (reported by al-Tirmidhi), along with the fact that النبي only performed العمرة when it coincided with his travels for الحج or other purposes, never making a journey solely for العمرة as a standalone obligation.
In practical terms, this scholarly difference has limited real-world impact because all four schools agree that performing العمرة is highly meritorious and strongly encouraged. النبي (صلى الله عليه وسلم) said, 'العمرة to العمرة is an expiation for the sins between them.' Even the Hanafi and Maliki scholars who classify it as السنة consider it one of the most highly مستحب acts of worship in Islam. Whether one follows the view that it is واجب or the view that it is السنة, the recommendation is the same: if you have the means and ability, you should perform العمرة at least once in your lifetime, and repeating it is a source of great reward.