Hadhrat Ammar bin Yaasir (Radhiyallaho anho) narrates that he heard the Prophet (Sallallaho alaihe wa-sallam) saying: "When a person finishes his salaat, he gets one tenth, one ninth, one eighth, one seventh, one sixth, one fifth, one fourth, one third or one half of the maximum reward (according to the quality of salaat performed by him)."
This shows that the reward is given in proportion to the sincerity and devotion with which salaat is performed. So much so, that some get only one tenth of the total reward. There are others who get a reward ranging from one tenth to one half of the maximum. It is also correct to say that there are some who receive the reward in full and there are others who get no reward at all.
It is stated in a hadith that Allah has a standard for fardh salaat. An account is kept of the measure by which a salaat falls short of that standard.
It is said in the hadith that devotion in salaat .will be the first thing to be taken away from the world. A time will come when not a single person in the whole congregation will offer his salaat with proper devotion.
Hadhrat Anas (Radhiyallaho anho) narrates that he I heard the Holy Prophet (Sallallaho alaihe wasallam) saying, "When a person offers his salaat at its fixed hours with proper wudhu, with humility and submission and with qiyaam, ruku and sajdah done satisfactorily, then such a salaat rises up in a bright and beautiful form and blesses the person in words: 'May Allah guard you as you have guarded me.' On the other hand, if a person is not punctual with his salaat nor does he perform wudhu, qiyaam, ruku and sajdah properly, then salaat rises up in an ugly and dark shape and curses the person saying, "May Allah ruin you as you have ruined me!" Then it is flung back like a dirty rag at the face of the person."
Lucky are those whose salaat is so perfect in all respects that this most important worship of Allah would pray for them. But what to say about the salaat which most of the people are wont? They go into sajdah direct from ruku, and they hardly lift their head from the first sajdah when they go for the second like a crow pecking at something. The curse that such a person deserves is mentioned in this hadith. When the salaat is cursing us then what else can check our downfall? This is why the condition of the Muslims is deteriorating day by day in every nook and corner of the world.
The same description is given in another hadith, with the addition that a salaat offered by a person with sincerity and devotion rises up highly illuminated, the gates of Heaven are let open for its reception, and then it intercedes (before Allah) for His devotee.
The Prophet (Sallallaho alaihe wasallam) has said, "The likeness of a person not bowing fully in ruku is that of a pregnant woman aborting just before delivery."
In a hadith, it is stated, "There are many fasting persons who get nothing out of their fast except hunger and thirst, and there are many worshippers who keep a vigil but get nothing from their vigil except sleeplessness.
Hadhrat Aa'ishah (Radhiyallaho anha) narrates that she heard the Prophet (Sallallaho alaihe wasallam) saying. "Allah has decided to save (from punishment of the Hereafter) a person coming before Him who has been offering salaat five times daily at its fixed hours, with due sincerity and devotion and with proper wudhu. As regards a person who does not so come before Allah, there is no guarantee for him. He may be forgiven by Allah's special Grace or taken to task.
Once the Prophet (Sallallaho alaihe wasallam) came to his companions and said, "Do you know what Allah has said?" The companions replied, "Allah and His Apostle know best." He repeated the question twice and the companions made the same reply each time. Then he said, "Allah says, 'By my Greatness and My Glory. I must bring into Paradise the person offering salaat five times daily at its fixed hours. As regards the person who does not ensure his salaat, I may forgive him by My mercy or take him to task.' "
Fazail-e-Amal by Maulana Muhammad Zakariyya
Vartues of Salaat - Chapter III - Quotations from the Hadith