What is the ruling on one who vowed to return to his old job after Hajj, and is he obligated to fulfill this vow?

The utterance of the aforementioned person is not considered a binding oath, and therefore, no expiation is required of him. This is because an oath is only binding when sworn by Allah Almighty Himself or by one of His attributes, as stated by Imam An-Nawawi. Consequently, this phrase is not considered an oath.