Should he clench his hand and point his index finger in the sitting between the two prostrations?
Question

                It was mentioned that sheikh Ben Uthaimeen - may Allah have mercy on him- said in a tape about the description of the prayer, that it is prescribed according to the Sunnah to raise and shake the index finger while sitting between the two prostrations, just like what we do in Tashahhud. The strange thing is that no other scholar has mentioned this I think except sheikh ben Uthaimeen. This opinion is not even in the description of the prayer in the book of Ash-sharh Al-Mumte’. Should I follow this opinion?.
Praise be to Allah.
    This is an issue concerning which there is a difference of 
    opinion among the fuqaha’. Some of them are of the view that the worshipper 
    should clench his right hand and point with his index finger in the sitting 
    between the two prostrations as he does during the tashahhud, and some of 
    them say that he should stretch out his hand and not clench it. 

    Ibn al-Qayyim (may Allaah have mercy on him) said: Then he 
    (blessings and peace of Allaah be upon him) raised his head, saying takbeer 
    but not raising his hands, and he lifted his head from prostration before 
    his hands, then he sat muftarishan, spreading out his left foot and sitting 
    on it, and holding his right foot upright. Al-Nasaa’i narrated that Ibn 
    ‘Umar said: One of the Sunnahs of prayer is to hold the right foot upright 
    with the toes facing towards the qiblah and to sit on the left foot. And 
    there is no report to suggest that the Prophet (blessings and peace of 
    Allaah be upon him) sat at this point in the prayer in any other way. 

    And he would place his hands on his thighs and place his 
    elbows on his thighs and the ends of his fingers on his knees, and he would 
    clench two of this fingers and make a circle, then he would raise his 
    finger, supplicating with it and moving it. This was said by Waa’il ibn 
    Hajar. Then he would say between the two prostrations: “O Allaah, forgive 
    me, have mercy on me, help me, guide me and grant me provision.” This is how 
    Ibn ‘Abbaas (may Allaah be pleased with him) narrated it from him (blessings 
    and peace of Allaah be upon him). Hudhayfah stated that he used to say: 
    “Lord forgive me, Lord forgive me.” End quote from Zaad al-Ma’aad, 
    1/230 

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said:

    With regard to the left hand, it should be laid flat with all 
    the fingers hand close together and pointing towards the qiblah and the edge 
    of the elbow should be at the end of the thigh, meaning that he should not 
    hold it away from the body; rather it should be resting on the thigh.  

    As for the right hand, the Sunnah indicates that he should 
    clench the pinkie finger and ring finger, make a circle with the thumb and 
    middle finger, and raise the forefinger, moving it when saying the du’aa’. 
    This is what it says in the reports from Imam Ahmad of the hadeeth of Waa’il 
    ibn Hajar, with an isnaad of which the author of al-Fath al-Rabbaani 
    said is jayyid. The commentator on Zaad al-Ma’aad said that it is 
    saheeh, and that was also the view of Ibn al-Qayyim. 

    As for the fuqaha’, they said that the right hand should be 
    laid flat when sitting between the two prostrations, like the left hand, but 
    following the Sunnah is better, and it is not narrated in the Sunnah in any 
    hadeeth, whether it be saheeh (sound), da’eef (weak) or hasan (good) that 
    the right hand should be spread out on the right thigh. Rather it is 
    narrated that it should be clenched; the pinkie finger and ring finger 
    should be clenched, and a circle should be made with the thumb and middle 
    finger, or the middle finger should also be clenched, and the thumb should 
    be clenched with it when sitting in prayer. Thus it was narrated in general 
    terms, and in some versions it says, “when he sits for the tashahhud.” Both 
    versions appear in Saheeh Muslim. So when we take the phrase “when he 
    sits in prayer”, we say: This is general and applies to all sittings, and 
    the words “when he sits for the tashahhud” in some versions do not refer to 
    that specific point in the prayer, because we have a principle which was 
    mentioned by the scholars of usool, and among those who always mentioned it 
    was al-Shawkaani in Nayl al-Awtaar and al-Shanqeeti in Adwa’ 
    al-Bayaan, among others, who say that if there is a report stating that 
    the ruling is broadly application and there is another report which mentions 
    that ruling in a specific situation, that does not mean that the second 
    report is specifying and limiting the application of the ruling mentioned in 
    the first report; rather the specifying and limiting is to be understood as 
    applying when a report refers to specific situations with a ruling different 
    from that which is applicable in regular situations. 

    An example of the first is if I tell you: honour the 
    students. This is general in meaning and includes all students. Then I tell 
    you: honour So and so - who is one of the students. Does this imply that I 
    should not honour other students? The answer is no, but it implies that 
    there is a particular reason why I singled him out for mention. 

    And an example of the second is if I say: honour the 
    students, then I say: do not honour So and so - who is one of the students. 
    This is specifying, because in the first case I mentioned So and so so as to 
    apply a ruling to him that is applicable to everyone, because he is one of 
    the students, but in the second case, I mentioned him so as to apply a 
    ruling different from the ruling that is applicable to everyone. Hence they 
    say when defining specification in the context of a ruling that is different 
    or when excluding some from that ruling: therefore a different ruling must 
    be applied to them. But if the ruling that applies to these is the same 
    ruling as is applicable to the others, the majority of scholars of usool 
    think that it does not indicate exclusivity for this group, as stated by the 
    author of Adwa’ al-Bayaan. This is clear, as in the examples that we have 
    given. Based on this, the fact that some of the versions of the hadeeth of 
    Ibn ‘Umar which refer to clenching the hand in the tashahhud only does not 
    mean that this is the only point in the prayer in which that is to be done, 
    because there are other reports which state that this is to be done in any 
    sitting in the prayer. End quote from al-Sharh al-Mumti’, 3/177. 

    Thus the evidence for this issue, and where it is to be found 
    in al-Sharh al-Mumti’, is clear to you. 

    And Allaah knows best.