The Position of the Hands in the Salah of the Prophet (pbuh)
We begin with the name of Allah who is the Most Merciful, the Bestower of Mercy. To proceed:
Sahl ibn Sa'd, may Allah be pleased with him, reported, "The people were ordered to place their right hand upon their left forearm." (Saheeh al-Bukhaaree, 1/102)
We can understand from this hadeeth that one should fold ones hands whilst in Salaah. Of course if the left hand were to be placed upon the left forearm as stated above then naturally, the hands would rest on the chest.
The forearm here means from the finger region of the hand right up to the elbow. In another hadeeth it is reported that, "He (sallelaho alaihi wa alaihi wasalam ) placed his right hand upon his left hand, wrist and forearm." (Sunan Nasaa'i with the footnotes of AllaamahSindhee(1/141),AbuDawood(1/112),lbnKhuzairnah(1/243,480) and Ibn Hibbaan (p.485) have all authenticated this narration).