Prostrating in a cap or turban, or when wearing gloves
Question

                Is it permissible to prostrate when wearing a cap if it covers the place of prostration on the forehead? Is it permissible to pray wearing gloves?.
Praise be to Allah.
    The scholars are agreed that it is better for a worshipper’s 
    forehead and hands to touch the ground directly when he prostrates, except 
    when he has an excuse. 

    They differed as to whether that is obligatory. Imam 
    al-Shaafa’i was of the view that it is obligatory, but the majority of 
    scholars are of the view that it is mustahabb only, and is not obligatory. 

    Al-Nawawi (may Allaah have mercy on him) said, explaining the 
    views of the scholars on this issue: 

    The views of the scholars with regard to prostrating on one's 
    sleeve, hem, hand, the end of one’s turban or anything else that is attached 
    to the person. We have mentioned that our view is that it is not correct to 
    prostrate on any of these things. This is also the view of Dawood and of 
    Ahmad, according to one report. 

    Maalik, Abu Haneefah, al-Awzaa’i, Ishaaq and Ahmad (according 
    to the other report) said that it is valid. The author of al-Tahdheeb 
    said: This is the view of the majority of scholars. They quoted as evidence 
    the hadeeth of Anas (may Allaah be pleased with him) who said: We used to 
    pray with the Messenger of Allaah  (peace and blessings of Allaah be 
    upon him) when it was intensely hot, and if one of us could not bear to 
    place his forehead on the ground, he would spread out his garment and 
    prostrate on it. Narrated by al-Bukhaari and Muslim.  

    It was narrated that Ibn 'Abbaas (may Allaah be pleased with 
    them) said: I saw the Messenger of Allaah (S) on a rainy day, avoiding the 
    mud when he prostrated by placing a garment that he was wearing beneath his 
    hands. Narrated by Ibn Hanbal in his Musnad.  

    It was narrated that al-Hasan said: The companions of the 
    Messenger of Allaah  (peace and blessings of Allaah be upon him) used to 
    prostrate with their hands inside their garments, and a man would prostrate 
    on his turban. Narrated by al-Bayhaqi. 

    And he said: The scholars are unanimously agreed that it is 
    preferable for the forehead to touch the ground directly when prostrating. 
    End quote from al-Majmoo’, 3/397-400 

    Ibn Qudaamah (may Allaah have mercy on him) said: The 
    worshipper does not have to touch the ground directly with any part of his 
    body. Al-Qaadi said: If he prostrates on the end of his turban, or on his 
    sleeve or hem, his prayer is valid according to one report. This is the view 
    of Maalik and Abu Haneefah. Those who allow prostrating on one’s garment 
    when it is too hot or too cold include ‘Ata’, Tawoos, al-Nakha’i, al-Sha’bi, 
    al-Awzaa’i, Maalik and Ishaaq. 

    Prostrating on the end of one's turban was allowed by 
    al-Hasan, Makhool, and ‘Abd al-Rahmaan ibn Yazeed. Shurayh prostrated on his 
    burnous. 

    End quote from al-Mughni, 1/305 
Shaykh Ibn ‘Uthaymeen 
    (may Allaah have mercy on him) was asked: If a worshipper prostrates and 
    puts his turban down as a protection between him and the ground, what is the 
    ruling on his prayer? 
He replied: The prayer 
    of that worshipper is valid, but he should not use his turban as a 
    protection between him and the ground except in cases of need, such as when 
    the ground is very hard, or there are stones that may hurt him, or thorns. 
    In that case there is nothing wrong with protecting himself from the ground 
    with something that is attached to him, such as his turban or clothing, 
    because Anas ibn Maalik (may Allaah be pleased with him) said: We used to 
    pray with the Prophet  (peace and blessings of Allaah be upon him) when 
    it was very hot, and if one of us could not put his forehead on the ground, 
    he would spread out his garment and prostrate on it. This indicates that it 
    is better to let the forehead touch the place of prostration directly, but 
    there is nothing wrong with a man protecting himself from the ground with 
    something that is attached to him such as his garment or turban, if there is 
    a need for that because the ground is very hot or very cold, or it is rough. 
    But he should remember that it is also essential to allow the nose to touch 
    the ground as well in this case, because of the hadeeth of Ibn ‘Abbaas (may 
    Allaah be pleased with him) who narrated that the Prophet  (peace and 
    blessings of Allaah be upon him) said: “I have been commanded to prostrate 
    on seven bones: the forehead” – and he pointed to his nose –“ the hands, the 
    knees and the ends of the feet.” End quote. 

    Fataawa al-Shaykh Ibn ‘Uthaymeen, 
    13/question no. 519 

    And Allaah knows best.