Faith is defined by Scripture in Hebrews 11:1
Now faith is the substance of that which is hoped for the evidence of accomplished deeds not seen.
Faith is always based upon a promise.
God has accomplished our salvation but we do not yet visibly see it. This does not mean we have no sight, it means we cannot at this time look at it. We can however see it in a way were we understand it, or see with discernment and therefore hope for when it will come, not if it will come.
Faith is taking God at His Word
He made a promise that He will keep. Faith is the basis for the hope that we have in Him and His promise to us.
For by grace you are in a state of being saved through the faith and this is not out from you; it [faith] is the gift from God.
because it has been given to you concerning Christ not only to believe in Him, but also to suffer concerning Him.
1 Corinthians 3:5
Therefore, who is Paul and who is Apollos but ministers through whom you believed and to each one as the Lord gave.
The manner of life, being sufficient, free of the fondness of money for the present for He, Himself, said, “I will never leave you nor ever forsake you.”
But if someone lacks wisdom, let him ask alongside the giving God to all simply and without reproach, and He will give it to him