We are to do things for God, not men. Be god pleasers, not men pleasers.
A lot of "christians" do things to be seen of other people, so they will look at them and say/think 'Oh, look at so-and-so, he is such a good chrisitian..'
*Pat on the back*
The pat on the back in 'their reward'. like this verse says. They won't receive any reward or recognition from God because he knows the true intentions of their hearts.
Sometimes, even things like praying in a public restaurant before you eat can be bad, if you are doing it for the wrong reasons.
A lot of ppl look at this verse and take it very literally. Like...ok we aren;t supposed to pray in the street and we need to go in our closets.....who prays in the streets?! no one.
They don't stop to think about all the other ways they can be doing things, now-a-days, just like these ppl. A lot of ppl go to church just so other ppl will see, or they only act godly in church....so other ppl will see, pray in restaurants, tithe, fake being nice at church, then gossip behind closed doors at home. The list goes on.
We need to seek gods approval, not mans'. And make sure that our intentions are pure. So that on judgment day he says 'well done, my good an faithful servant.'
Because believe me everyone....no one is fooling God. He is not mocked.