I have read somewhere that Allah(Azawajal) takes away parts of prayer based on how much much one is concentrating.. I would like to know if there is a hadith which states this and if it is sahih.
Here some findings which might be relevant:
If one doesn't do his prayer well (correct wudu, on time, take his time for each movement), might or might not be pardoned by Allah.
Narrated Abdullah ibn Sunabihi:
AbuMuhammad fancies that witr prayer is essential. (Hearing this) Ubadah ibn as-Samit said: AbuMuhammad was wrong. I bear witness that I heard the Messenger of Allah (ﷺ) say: Allah, the Exalted, has made five prayers obligatory. If anyone performs ablution for them well, offers them at their (right) time, and observes perfectly their bowing and submissiveness in them, it is the guarantee of Allah that He will pardon him; if anyone does not do so, there is no guarantee for him on the part of Allah; He may pardon him if He wills, and punish him if He wills. (sunan abi Dawod)
Prayer is (rather) invalid if one doesn't do a correct prostration and ruku':
On Islamonline there was a Fatwa asking about a statement "ليس للمرء من صلاته إلا ما عَقَل منها" whether it is a hadith or not. The statement can be translated as follows:
A person only earns or get rewarded for what he remembered of his prayer
The answer there says that this is a statement from al-Ehya' of Imam al-Ghazali which was commented by al-'Iraqi (The hadith hafidh who examined and qualified etc. the ahadith of this book) who said: I've bever found it marfo' (as saying of sahabi who attributed it to the Prophet (). But the meaning seems to go ahead with other statements.