“If you had faith like a grain of mustard seed, you would tell this sycamore tree, Be uprooted and planted in the sea, and it will obey you – Luke 17:6 (Messianic).
Faith is simply believing and acting on the words and integrity of another. Faith in God is to believe and act on what He says in His Word, the Bible.
The Words of Jesus in the Gospel of Mark advise us to have faith in God:
“Truly tell, you, if anyone says to this mountain, Go, throw yourself into the sea, and does not doubt in their heart but believes that what they say will happen, it will be done for them – Mark 11:22-23
Jesus is saying in essence, Have a God kind of faith. Don’t put your faith in your own faith, or the faith of other people, or the mountains, or in anything that you expect to happen because of your faith. Put your faith in God, because it’s your faith in Him that will accomplish the moving of mountains. You can’t speak to the mountain and expect it to move unless you are connected to God. Apart from Him, you don’t have the power to complete such monumental tasks.
Believing in God means believing in His Word. For faith to work, you believe, confess, and act upon what the Word of God says about your situation.
From Pity to Praise 