All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Whoever lives in Riyadh and wants to perform 'Umrah has to assume his Ihraam from the Meeqaat, Wadi Al-Sayl (a place designated by The Prophet, sallallaahu ‘alayhi wa sallam, to assume Ihraam from) if he is traveling by road. As for those traveling by air, then they assume Ihraam whenever they pass over any Meeqaat area.
One cannot delay his Ihraam until he reaches Jeddah even if he intends to visit his relatives or to stay there for his work. This is based on the saying of the Prophet, sallallaahu ‘alayhi wa sallam: “The residents of Madeenah should assure the Ihraam from Thul-Hulayfah, the people of Syria from Al-Juhfa and the people of Najd from Qarn. And these Mawaaqeet (plural Meeqaat) are for the residents of those places, and for travelers who come through those places (or parallel to them) with the intention of performing Hajj and 'Umrah." [Al-Bukhari and Muslim]
The person who passes by the Meeqaat without assuming Ihraam and does not return to it to assume Ihraam from the Meeqaat before performing his rituals must slaughter a sheep as expiation, and should distribute its meat among the poor of Makkah.
The above ruling is for whoever decided to perform 'Umrah and crossed the Meeqaat without assuming the state of Ihraam. If one was hesitant in his decision of 'Umrah and did not firmly decide to perform 'Umrah after completing his commitments in Jeddah, and thereafter he decided to perform 'Umrah, in this case he can assume his Ihraam from the place where he is staying, i.e. Jeddah. This is for the narration that the Prophet, sallallaahu ‘alayhi wa sallam, said: "And whoever is living within these boundaries can assume Ihraam from the place he starts, and the people of Makkah can assume Ihraam from Makkah."
Allaah Knows best.