'Ammar Ibne-Yasir Radiyallahu 'anhuma narrates: I heard Rasullullah Sallallahu 'alaihi wasallam saying: Indeed a person completes his Salat and only one-tenth of the maximum reward, is written for him. Likewise for some one-ninth, one-eighth, one-seventh, one-sixth, one-fifth, one-fourth, one-third or half of it is written. (Abu Dawud: 796)
Note: The Hadith explains that the more the outward appearance and
the inner devotion in Salat corresponds to Sunnah, the greater is the
reward. (Badhl-ul-Majhud)