This is a well-known point of scholarly disagreement among the four schools. The Shafi'i and Hanbali schools hold that Umrah is obligatory (wajib) once in a lifetime for every Muslim who has the physical and financial ability — similar to Hajj but without the specific time restriction. The Hanafi and Maliki schools consider Umrah to be a confirmed Sunnah (Sunnah mu'akkadah) that is highly recommended but not obligatory.
Sheikh Ibn Baz held the position that Umrah is obligatory once in a lifetime, following the Hanbali and Shafi'i position. He cited the hadith where a bedouin asked the Prophet about Umrah: 'Is Umrah obligatory?' and the Prophet said: 'No, but if you perform Umrah, it is better for you.' However, he noted that other narrations and the Quran's command 'And complete the Hajj and Umrah for Allah' support the obligation. He reconciled the evidence by concluding that Umrah is obligatory.
Sheikh Al-Fawzan similarly held Umrah to be obligatory, stating that the conjunction of Umrah with Hajj in the Quranic verse — 'And complete the Hajj and Umrah for Allah' (Al-Baqarah, 2:196) — indicates that they share the same ruling of obligation. He acknowledged the opposing view but considered the evidence for obligation to be stronger. Those who hold Umrah to be Sunnah note that the Prophet's statement 'No' in response to 'Is it obligatory?' is explicit, while those who hold it obligatory interpret that hadith differently.