Hadith 8:368
Abu Bakr narrated to us, he said: Whoever performs Umrah during the months of Hajj then returns, he is not a Mutamatti (one performing Tamattu). That is for the one who stays and does not return.
حدثنا أبو بكر قال من اعتمر في أشهر الحج ثم رجع فليس بمتمتع ذلك من أقام ولم يرجع