Shaikh al-Albani rahimahullah said:
“Building upon that, you find in some of the Arab lands, rather in some of the Schools of thought which are followed, [the mention of] of placing the right hand upon the left on the heart and not on the chest [in prayer]. This is against the Sunnah. The Sunnah is to place them upon the chest and not to place them on the heart, which the Prophet (ﷺ) described with his statement:
ألا وإن في الجسد مضغة إذا صلحت صلح الجسد كله وإذا فسدت فسد الجسد كله ألا وهي القلب
There is a piece of flesh in the body if it becomes good (reformed) the whole body becomes good but if it gets spoiled the whole body gets spoiled and that is the heart.
So it is not from the Sunnah is to place the hands like this, inclining them towards the left. Verily, the Sunnah is to place them like this upon the chest. So whoever takes them to the left due to a philosophical explanation has no foundation. Verily, it is the that the heart is the center of Iman. So placing the hands upon the chest is from the angle of preserving the Iman whose place of settlement is the heart. These explanations, for which Allah did not sent down an authority, are not reported in any Hadith, not even a weak Hadith or a fabricated Hadith from the Prophet (ﷺ) that the Prophet (ﷺ) used to incline to the heart when placing his hands on his chest like this. So you find some incline when placing his hands like this, then he comes with his forearm under his armpit. The Sunnah is to place the hands on the chest and not incline them to the left on the heart. So inclining them to the left on the heart, like the one who does this, does not have an origin for this or this. Verily, the hands are placed on the chest. It has come in some books of tafseer that the Prophet (ﷺ) explained His statement:
إِنَّا أَعْطَيْنَاكَ الْكَوْثَرَ فَصَلِّ لِرَبِّكَ وَانْحَرْ
Verily, We have granted you (O Muhammad (Peace be upon him)) Al-Kauthar (a river in Paradise); Therefore turn in prayer to your Lord and sacrifice (to Him only).
He said: (انحر) that is: place your hands on your chest. So the chest is here and not here. This is what I loved to mention between the answer to your question”.
[Fatawa al-Judda no. 16 Side A]
Faisal Ibn Abdul Qaadir Ibn Hassan