Is Ḥajj immediately obligatory upon the one who is able [to perform it]?

Q. Is the obligation of Ḥajj to be performed immediately or eventually [i.e. whenever one wishes]?

A. The correct position is that it is an immediate obligation, and that it is impermissible for a person who is capable of performing Ḥajj to Allāh’s House to delay it. The same goes for all acts of obligations in the Sharīʿah; if they are not restricted by time or a cause then they are immediate obligations.

Ibn ʿUthaymīn, Majmūʿ Fatāwā wa Rasāʾil (13/21)