Just before revealing His covenant with the nation of Israel through Moses, it is God Himself who defines what faith means:

"'You yourselves have seen what I did to the Egyptians, and how I bore you on eagles' wings, and brought you to Myself. Now then, if you will indeed obey My voice and keep My covenant, then you shall be My own possession among all the peoples, for all the earth is Mine; and you shall be to Me a kingdom of priests and a holy nation.' These are the words that you shall speak to the sons of Israel." (Ex 19:4-6)

1. Believe that Yahweh is alive and historically real ("you yourselves have seen what I did to the Egyptians").

2. Trust that engenders an obedience to God's word ("if you will indeed obey My voice and keep My covenant").

The Exodus becomes the historical event that establishes the reality of the invisible God and is the preamble to the Ten Commandments, which is read at least annually with the Decalogue, to remind the Israelites of the reality of God through His historical work (Ex 20:2).

Faith has a basis in historical fact with a view towards the future as God fulfills His covenants.

Abraham (Gen 15:6) is noted as a great example of faith in the New Testament (Rom 4:3; Gal 3:6; James 2:23).

Abraham leaves his home, from Haran to Egypt, on God's verbal promise of the future (Gen 12:1-4).

Despite the age of him and his spouse, Abraham believes in God's promise of an heir (Gen 15:6).

Abraham had no historical basis that God was real!

For his faith, God declares Abraham "righteous" and appropriate for a covenant relationship; the unilateral and unconditional Abrahamic Covenant results. God identifies Himself as "the God of Abraham" (Ex 3:6) and Abraham is known as "God's friend forever" (2 Chron 20:7).

For deeper study:

What are the themes of "faith" in the Old Testament?