So if this addition was present in the
    ‘Musannaf’ he would have mentioned it, and his works are replete with quotes
    from it. And this is ibn Ameer al-Haaj, who outdid his shaykh ibn al-Hammaam in research
    and depth of investigation, saying in ‘Sharh al-Maniyyah’, ‘What is
    established in the Sunnah is to place the right hand upon the left in prayer, and there is
    no authentic hadeeth that establishes the place of placing them on the body except the
    aforementioned hadeeth of Wa’il.’ So if this hadeeth were present with this
    addition, Ibn Ameer al-Haaj would have mentioned it especially since his commentaries are
    overflowing with quotes from the ‘Musannaf’." [End of quote from as-Sindee]
I say (in conclusion): the aforementioned hadeeth of
    Wail bin Hujr even though it’s sanad is good, there is a severe problem in affirming
    the wording, ‘below the navel’ as you have come to know.
2) The hadeeth of Alee (RA) 
 reported by Abu
    Dawood, Ahmad, ibn Abee Shaybah, ad-Daaruqutnee, al-Bayhaqee and Abu Juhayfah that Alee
    said, ‘the Sunnah is to place the hand upon the hand below the navel.’
I say: it’s isnaad contains Abd ar-Rahmaan
    Ishaaq al-Waasitee, and this hadeeth revolves around him. And he is da’eef and it is
    not correct to depend upon him. al-Haafidh az-Zayla’i said in ‘Nasb
    ar-Raayah’ after mentioning this hadeeth, ‘ibn Qattaan said, "Abd
    ar-Rahmaan bin Ishaaq, he is ibn al-Harb Abu Shaybah al-Waasitee and ibn Hanbal and Abu
    Haatim said about him, "rejected in hadeeth." And ibn Ma’een said, "he
    is nothing." And Bukhaaree said, "there is a problem in him." And
    al-Bayhaqee said in ‘al-Ma’rifah’, "it’s isnaad is not authentic,
    And ar-Rahmaan bin Ishaaq al-Waasitee is alone in reporting it and he is abandoned."
    And an-Nawawee said in ‘al-Khulaasa’ and ‘Sharh Saheeh Muslim’,
    "and it is a hadeeth which is weak by agreement for Abd ar-Rahmaan bin Ishaaq is weak
    by agreement."’
And Shaikh ibn al-Hammaam said in
    ‘at-Tahreer’, ‘when al-Bukhaaree says about someone, "there is a
    problem in him" then his hadeeth are not depended upon or used for support, or given
    any consideration.’
So when you come to know all of this, it becomes
    clear that this hadeeth of Alee is not to be depended upon, or used as support or given
    any consideration. Then it also contradicts the tafseer of Alee to the saying of Allaah,
    "wanhar" that he placed his hand upon the center of his left forearm and placed
    them upon his chest - reported by al-Bayhaqee, ibn Abee Shaybah, ibn al-Mundhir, ibn Abee
    Haatim, ad-Daaruqutnee, Abu ash-Shaykh, al-Haakim and ibn Mardawiyyah as in ‘ad-Durra
    al-Manthoor’.
al-Faadil Mulla al-Haddaad said in ‘Haashiyah
    al-Hidaayah’, ‘so when the hadeeth of placing the hands below the navel is weak,
    and contradicts the narration of Alee that he explained His saying, "wanhar", by
    placing the right hand upon his left on his chest then it is obligatory to act upon the
    hadeeth of Wa’il which an-Nawawee mentioned. Then this (da’eef) hadeeth of Alee
    is also to be considered abrogated according to the way of the Hanafiyyah. The author of
    ‘ad-Durra fee Idh’haar Gash Naqd as-Surra’, and he is Hanafee in madhab,
    said, "Abu Dawood reports on the authority of Jarir ad-Dabbi that he said, ‘I
    saw Alee placing his right hand upon his left wrist above the navel.’ So the
    principle of our scholars is that when the Companion acts contrary to what he narrates
    then this indicates the abrogation of what is narrated.’
I say: the isnaad of the narration of Alee, I mean
    the one that Abu Dawood relates from Jarir ad-Dabbi is saheeh as you will come to know.
3) The hadeeth of Abu Hurayra reported by Abu
    Dawood from Abu Waa’il who said, ‘Abu Hurayra said, hold the hand with the hand
    below the navel.’ I say: the isnaad of this hadeeth also contains Abd ar-Rahmaan bin
    Ishaaq al-Waasitee. So this hadeeth is also not fit to depend upon, or use as a support or
    give any consideration to as you have just come to know.
4) The hadeeth that ibn Hazm mentions in
    ‘al-Muhalla’ in ta’leeq form from Anas with the wording, ‘three are
    from the manners of the Prophethood: hastening the iftaar, delaying the suhoor, and
    placing the right hand upon the left below the navel in the prayer.’
I say: I have not come across the sanad of this
    hadeeth, and the Hanafee scholars mention it in their books and depend upon it but they do
    not mention it’s isnaad. And if the isnaad of something is not known then it is not
    correct to depend upon it, or use it as support or give it any consideration.