1 John 5:14-15 (NIV)
14This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us.
15And if we know that he hears us–whatever we ask–we know that we have what we asked of him.
John 15:7 (ESV)
If you abide in me, and my words abide in you, ask whatever you wish, and it will be done for you.
James 5:16 (NIV)
16Therefore confess your sins to each other and pray for each other so that you may be healed. The prayer of a righteous man is powerful and effective.