Trusting God and taking Him at His word.
Faith is the substance of things hoped for, the evidence of things not seen. It comes by hearing the word of God and shows itself in obedience.
What the Scriptures say
Now faith is the substance of things hoped for, the evidence of things not seen. Hebrews 11:1 · KJV
But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him. Hebrews 11:6 · KJV
So then faith cometh by hearing, and hearing by the word of God. Romans 10:17 · KJV
Even so faith, if it hath not works, is dead, being alone. James 2:17 · KJV