Joining Hajj with ‘umrah before shaving the head
Question

                If the pilgrim who is doing tamattu‘ (‘Umrah followed by Hajj, exiting ihram in between) enters ihram from the miqaat, then does the rituals of ‘umrah, then does not exit ihram afterwards, but remains in ihram with the intention of doing Hajj, what is the ruling on that?
Praise be to Allah.
    If what you mean by saying “[he] does not 
    exit ihram afterwards” is that he did tawaaf and sa‘i for ‘umrah, and shaved 
    his head or cut his hair, but he did not take off the ihram garments; rather 
    he entered ihram for Hajj straight away, in the ihram garments he had worn 
    for ‘umrah, there is nothing wrong with that, because he is doing tamattu‘, 
    and he finished the actions of ‘Umrah then entered ihram for Hajj. So his 
    ‘Umrah is valid and so is his Hajj. But if he entered ihram for Hajj before 
    the day of at-Tarwiyah (8th Dhu’l-Hijjah), then he was too hasty, 
    but the most that can be said is that he went against the Sunnah by 
    hastening. However there is no blame for that, and he has to offer a 
    sacrifice because he is doing tamattu‘, just like anyone else. 

    But if what you mean by saying “[he] does 
    not exit ihram afterwards” is that he joined Hajj to his ‘Umrah after he did 
    tawaaf and sa‘i for ‘umrah and before shaving his head or cutting his hair, 
    then in this case there is a difference of scholarly opinion concerning the 
    matter. The most well-known view in our madhhab is that his Hajj is not 
    valid, because it is not valid to join Hajj to ‘Umrah after starting the 
    tawaaf of ‘umrah, because he began the process of exiting ihram for ‘Umrah 
    by doing that. This was clearly stated by the fuqaha’ (may Allah have mercy 
    on them) – except in the case of one who has a hadiy (sacrificial animal) 
    with him. 

    There is a second opinion which was 
    mentioned by al-Muwaffaq in al-Mughni and others, which is that his 
    Hajj is valid, but he must offer a compensatory sacrifice, and thus he will 
    be doing qiraan (‘Umrah followed by Hajj without exiting ihram in between). 
    It says in al-Mughni (5/244): If he enters ihram for Hajj before 
    cutting his hair, then he has joined Hajj to ‘Umrah, so he is now doing 
    qiraan. End quote. However it should be noted that al-Muwaffaq had 
    previously stated that this is not valid. 

    The scholars were not certain about that 
    comment. Some of them said that this was forgetfulness on the part of al-Muwaffaq 
    (may Allah have mercy on him), and others said that it was not 
    forgetfulness; rather he followed a different opinion. Yet others said that 
    what is meant is the one who has a hadiy with him. The view that his Hajj is 
    valid is the view of the Maalikis and those of the Hanbalis who held this 
    view: al-Muwaffaq in al-Mughni, and the authors of ash-Sharh al-Kabeer 
    (3/424), al-Mustaw‘ib (4/291) and al-Mubdi‘ (3/327). It was 
    also the view of Shaykh Abu’l-Mawaahib and Shaykh Sulaymaan ibn ‘Ali, who 
    mentioned it in Mufeed al-Anaam and favoured this view in cases where 
    the person forgot or was ignorant of the ruling, but he has to offer a 
    compensatory sacrifice for having not shaved his head or cut his hair 
    (following ‘Umrah). And Allah knows best. 

    Shaykh ‘Abdullah ibn ‘Abd al-‘Azeez ibn ‘Uqayl. 

    Shaykh Ibn ‘Uthaymeen (may Allah have 
    mercy on him) favoured the view that his Hajj is valid and he is (still) 
    doing tamattu‘, based on his intention. But he has to offer a sheep because 
    he omitted one of the obligatory acts of ‘Umrah, namely shaving the head or 
    cutting the hair. He (may Allah have mercy on him) was asked: If the one who 
    is doing tammatu‘ forgets to cut his hair, then he begins Hajj and remembers 
    after beginning Hajj, what is the ruling? 

    He replied: 

    This is a serious matter. Some of them 
    said that his Hajj does not count, because he entered ihram for Hajj the 
    wrong time. If he wanted to do qiraan, he should have entered ihram for Hajj 
    before doing tawaaf. So now he is not doing qiraan or tamattu‘. But what we 
    think is that he is doing tamattu‘, but he must offer a fidyah for failing 
    to cut his hair, and his Hajj is valid, in sha Allah.

    End quote from Fataawa Ibn ‘Uthaymeen 
    (22/474, 475)

    And Allah knows best.