It is the greatest trust of God-Almighty and is the criteria...

It is the greatest trust of God-Almighty and is the criteria of acceptance of all other deeds. The prayer is such a mysterious heavenly formula, but subjected to its being alive and possessing spirit, which means heart's presence during prayer, paying attention towards God-Almighty, and being humble in front of Him.

The invocations, recitals of Qur’anic verses, genuflection, prostration, the witnessing, and salutations constitute the face and body of the prayer while the heart's presence and attention towards the Creator form its spirit.

Since a body without a soul becomes a dead body lacking any characteristic, likewise a prayer offered without heart's presence, although satisfies as far as the performance of compulsory religious obligation is concerned, nevertheless, such a prayer does not help in ascending the prayer offerer towards higher spiritual positions. In principle, the greatest objective behind the establishment of prayer may be described as -invocation recitals and engaging in God's Remembrance.

(62: 9) The criteria for the acceptance of prayer is -the heart's presence, and whatever amount of heart's presence it may contain, the prayer will be accepted accordingly. It is because of this consideration that traditions have emphasized a lot about the importance of heart's presence in prayers.

For example: The Holy Prophet (S) has said: قال النبى صلى الله عليه وآله: ان من الصلاة لما يقبل نصفها وثلثها وربعها وخمسها إلى العشر, وان منها لما تلفّ كما يلفّ الثوب الخلق فيضرب بها وجه صاحبها, وانما لك من صلاتك ما اقبلت عليه بقلبك. “Sometimes only half of the prayer gets accepted while at other times may be one-third, one fourth, one-fifth, and one-tenth of it will be accepted. Some of the prayers like an old wrapped cloth are pounded upon the offerer's head.