As for Jeddah, it is not a miqāt except for its own residents and for anyone who first forms the intention to perform the rites while already there. Therefore, if you come from Yemen intending ʿUmrah, you must enter into ihram at the miqāt you encounter on your route and not postpone it until Jeddah. Should you pass the miqāt and only assume ihram in Jeddah, a dam (compensatory sacrifice) becomes obligatory upon you, for you have neglected a duty—namely, entering into ihram at the miqāt you crossed. Whoever abandons a duty must offer a dam.
Since you have been entering into ihram from Jeddah while travelling from Yemen with the intention of ʿUmrah and have been passing the miqāt each time, a fidyah (expiation) is due from you on every such occasion. This fidyah is the slaughter of a sheep, the meat of which you must distribute in Makkah to the poor of the Sacred Precinct, keeping none of it for yourself. It compensates for the shortcoming in your rite. Your ʿUmrah remains valid, but you need this compensation as described, and the obligation is incurred each time you begin ʿUmrah from Jeddah after bypassing the miqāt.
Question: Suppose this happens—someone comes intending ʿUmrah, or perhaps for another purpose, and he passes the miqāt at which he should have entered into ihram, then learns the ruling before beginning the rites of ʿUmrah. What should he do in such a case?
Answer: If he has already assumed ihram after passing the miqāt, a dam is binding upon him and he is to proceed with his rite.
Question: In other words, he does not have to return to the miqāt in addition to offering the dam?
Answer: Returning will not benefit him, even if he were to go back. There is no need to return; once he has entered into ihram the matter is settled. He should slaughter the fidyah and continue with his rite.
However, if he remembers before entering into ihram and then returns to the miqāt and assumes ihram from there, he has fulfilled the duty and nothing is required of him.