rewards against going for the fard salah.

the reward of the man who purifies himself and goes out of his house to offer the fard salah is like the pilgrim's who assumes the ihram.
the reward for the person who prepares for the duhu (or chaast) salah, without having in mind anything besides that, is like the reward for one who performs umrah.
a salah which follows another salah without indecent and vain talk inbetween is recorded in the illiyyeen. {ahmad}. ref..the pearls of hadith. darul ishaat