He did ‘umrah as part of Hajj tamattu‘, then he went out of Makkah; does he have to come back in ihraam for Hajj?

He does not have to enter ihraam [at that point]. If the one who is doing tamattu‘ does ‘umrah, then goes out from Makkah to at-Taa’if or Jeddah or Madinah, then comes back, he does not have to enter ihraam for Hajj (yet), because he has come back to the place where he is staying. As he has come as a pilgrim, Makkah is regarded as the place where he is staying, so if he travels to Madinah then comes back, he has come back to the place where he is staying. Therefore he should enter ihram for Hajj on the day of at-Tarwiyah [i.e., 8^th Dhu’l-Hijjah] from Makkah, as if he is one of the residents of Makkah who went to Madinah during the months of Hajj, then came back from Madinah having the intention to do Hajj this year. So he does not have to enter ihram for Hajj from anywhere other than Makkah. End quote.

Majmoo‘ Fataawa Ibn ‘Uthaymeen (22/78).