What you are looking for is this:
Matthew 6:5,6
5 “And when you pray, you shall not be like the hypocrites. For they love to pray standing in the synagogues and on the corners of the streets, that they may be seen by men. Assuredly, I say to you, they have their reward. 6 But you, when you pray, go into your room, and when you have shut your door, pray to your Father who is in the secret place; and your Father who sees in secret will reward you openly.
I gave it to you in context. Hopefully you are using it as an educational opportunity and not as a reverse attack; there are passages in the Bible about that too. To do so would make you no better than those you might direct this passage to.
I know my stuff when it comes to this, ask anyone here, they have been vexed more than once by it.