Reward of prayer is based on its inward and outward perfection
23-7-2006 | IslamWeb
Question:
Please tell us some ways by which khushoo' in salaat and other 'ibaadaat can be improved. Is the Hadeeth referring to a worshipper leaving his place of worship while his gets a tenth, ninth eighth, etc of his salaat referring only to the reward commensurate with the amount of khushoo' in that salaat or the all aspects of the salaat?
Answer:
All Perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as that of his family and all his companions.
Allaah commands us to establish the prayers, He Says (what means): {And establish prayer}[Quran 2:43]. Establishing prayers implies establishing them inwardly and outwardly. Establishing the prayers outwardly is done by fulfilling their prerequisites, pillars, and obligations. Establishing them inwardly is done by humbling ourselves, and having attentiveness and submissiveness in the heart and mind. Submissiveness is the sprit of the prayer. As a matter of fact, the praying person only gets the reward of that portion of his prayer which he performed attentively.
Imaam Ibn Al-Qayyim 
said: ‘The righteous predecessors agreed by consensus that the praying person only gets the reward of that portion of his prayer which he performed attentively.’
In this regard, we have issued a Fatwa about the means that helps achieving the submissiveness in prayers; see Fatwa 85048.
Furthermore, the narration that you referred to in your question is narrated by 'Ammaar bin Yaasir 
who said: 'I heard the Prophet 
saying: "A praying person may end his prayer while only the reward of one tenth of it is recorded for him, or one ninth of it, or one eighth of it, or one seventh of it, or one sixth of it, or one fifth of it, or one fourth of it, or one third of it, or half of it." [Ahmad and Abu Daawood]
As can be seen clearly, the reward of the prayers is based on both the outward and inward performance of it, and not on submissiveness alone. Therefore, Imaam Al-Atheemabaadi wrote clarifying the reason for the prayer's reduction of reward: ‘Due to what he missed of its the pillars, prerequisites, humbleness and submissiveness.’
Allaah Knows best.