¥Not to let God know our needs; God already knows what we will pray for.
–Matt 6:31 (NIV) So do not worry, saying, "What shall
we eat?" or "What shall we drink?" or
"What shall we wear?" 32 For the
pagans run after all these things, and your
heavenly Father knows that you need them.
¥Not to get God to change His mind; if it isn't His will, you won't get it.
–Matt 26:39 (NIV) Going a little farther, he fell with his
face to the ground and prayed, "My Father, if it is possible, may this cup be taken from me. Yet not as I will, but as you will."