In the Bible, particularly in the New Testament, and specifically in Hebrews, faith is all about the Finished Work of Jesus Christ, that when He declared "It is Finished!" (John 19: 30), He was not lying, He was not joking, and more importantly, that there was not something more which we needed to offer.
Faith is all about the Cross, and everything that He bought for us there:
"Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed." (1 Peter 2: 24)
For the Old Testament Saints, faith was to believe in what God would do through His Son. They were believing "for":
"3He is despised and rejected of men; a man of sorrows, and acquainted with grief: and we hid as it were our faces from him; he was despised, and we esteemed him not.
4Surely he hath borne our griefs, and carried our sorrows: yet we did esteem him stricken, smitten of God, and afflicted.
5But he was wounded for our transgressions, he was bruised for our iniquities: the chastisement of our peace was upon him; and with his stripes we are healed." (Isaiah 53: 3-5)
The next chapter spells out what will happen:
14In righteousness shalt thou be established: thou shalt be far from oppression; for thou shalt not fear: and from terror; for it shall not come near thee.
15Behold, they shall surely gather together, but not by me: whosoever shall gather together against thee shall fall for thy sake.
16Behold, I have created the smith that bloweth the coals in the fire, and that bringeth forth an instrument for his work; and I have created the waster to destroy.
17No weapon that is formed against thee shall prosper; and every tongue that shall rise against thee in judgment thou shalt condemn. This is the heritage of the servants of the LORD, and their righteousness is of me, saith the LORD." (Isaiah 54: 14-17)
For the Old Testament prophets, they were looking forward to the Coming of the Lord, the Messiah:
"1For, behold, the day cometh, that shall burn as an oven; and all the proud, yea, and all that do wickedly, shall be stubble: and the day that cometh shall burn them up, saith the LORD of hosts, that it shall leave them neither root nor branch. 2But unto you that fear my name shall the Sun of righteousness arise with healing in his wings; and ye shall go forth, and grow up as calves of the stall. 3And ye shall tread down the wicked; for they shall be ashes under the soles of your feet in the day that I shall do this, saith the LORD of hosts." (Malachi 4: 1-3)
That day prophesied by Malachi, was fulfilled in Christ, when He was born of a virgin, framed in human flesh, then died on the Cross to be seated at the right hand of God the Father (Ephesians 2: 1-6)
Today, we are not believing for God to do something, but we are called to believe from Him, that He has taken care of everything:
"31What shall we then say to these things? If God be for us, who can be against us? 32He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things? 33Who shall lay any thing to the charge of God's elect? It is God that justifieth. 34Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us." (Romans 8: 31-34)
What can we believe from Him today?