The majority of scholars say الحج must be performed immediately when able — delaying without valid reason is sinful; the Shafi'i school permits delay but recommends haste.
There is a scholarly difference of opinion on whether الحج must be performed immediately once the conditions of obligation are met. The majority position (held by the Hanafi, Maliki, and Hanbali schools) is that الحج is an immediate obligation (واجب ala al-fawr) — once a person has the financial means, physical health, and safe passage, they must perform it at the earliest opportunity. Delaying without a valid excuse is considered sinful عند this majority view.
The Shafi'i school takes a slightly different position, holding that الحج is an obligation that may be fulfilled at any point during one's lifetime (واجب ala al-tarahi), though performing it sooner is preferred and مستحب. However, even Shafi'i scholars caution against excessive delay due to the uncertainty of life. النبي (صلى الله عليه وسلم) said: 'Hasten to perform الحج (meaning the واجب الحج), for none of you knows what may happen to them' (Ahmad, with a sound chain). Valid reasons for delay include genuine illness, unsafe travel conditions, legal visa restrictions, and unresolved financial obligations.
Source: مسند أحمد; al-Nawawi, al-Majmu'; ابن قدامة, al-Mughni; al-Kasani, Bada'i al-Sana'i