Moses remained in Midian for forty years (Acts 7:30). God used the first forty years of Moses’ life to build up a man who was strong in the natural life (Acts 7:22; vv. 11-13). Then, in order to strip Moses of his natural ability, God arranged to have him work as a shepherd in the land of Midian for another forty years (Exo. 3:1). God’s work to perfect Moses made him a useful vessel for God’s purpose.
According to Exodus, being useful to God is related to building up His dwelling place and to fighting for His interests on earth. Chapters 1 and 2 show that the life useful to God in these matters is the life signified by the female life. In the Bible a male signifies an independent life, whereas a female signifies a life that depends on God (cf. Luke 1:26-38). The unique male is God in Christ; only He has an independent life. In their relationship to God all God’s people, both men and women, are “females,” components of His wife (Isa. 54:5; John 3:29). As such, they must live a life that depends on Him for everything and is under His headship (John 15:5; 1 Cor. 11:3). At the age of forty Moses lived an independent life, taking the position of a “male” before God by exercising his natural strength to strike an Egyptian (vv. 11-12). In the second forty years of his life Moses was trained by God not to rely on his natural life, and in his third forty years he lived the life of a “female,” a life dependent on God. This is the life God can use for the fulfillment of His purpose.