Is it impermissible for a resident of Makkah, who left for Dammam for work then returned to Makkah, to enter into a state of ihram for Hajj from his home or from the Miqat of Sayl al-Kabeer?

There is no need to assume ihram when returning to Makkah if there is no intention to perform a ritual, and this is the most preponderant opinion. However, if one intends to perform Hajj, ihram must be assumed from Makkah itself, based on the Prophet's (peace be upon him) saying: "And whoever is within [the prescribed boundaries of the miqats], then from where he originates, even the people of Makkah [assume ihram] from Makkah."