None of you should pray in a single garment with nothing on his shoulders

Explanation

The Prophet (may Allah's peace and blessings be upon him) prohibited the one praying in a single garment from leaving his shoulders, i.e., what is between the shoulder and the neck, uncovered without putting anything on them to cover them. This is because although the shoulders are not ‘Awrah (must-cover body parts), yet covering them guarantees better concealment of the ‘Awrah, besides being closer to showing reverence and glorification to Allah Almighty while standing before Him in prayer.

Benefits

• It is permissible to pray in a single garment if it covers what must be covered.
• It is permissible to pray in two garments, one covering the upper part of the body and the other covering the lower part.
• It is recommended for the person praying to be in a good and presentable state.
• It is obligatory to cover the shoulders or one of them during the prayer if possible, and it is said that it is not strictly forbidden.
• The Companions (may Allah be pleased with them) had little money to the extent that some of them did not possess two garments.
• An-Nawawi said, commenting on the meaning of the Hadīth: The rationale behind this is that if he used it as a lower garment without having anything thereof on his shoulder, his ‘Awrah may be revealed; however, this will not be the case if he puts part of it on his shoulder. Moreover, he might need to hold it with his hand or with both hands and would, thus, miss the act of Sunnah of putting the right hand on the left one below his chest, raising both hands as prescribed, etc. In addition, this entails refraining from covering the upper part of the body and the place of adornment, and Allah Almighty says: {Dress well for every prayer.} [Surat al-A‘rāf: 31]