The number 40, as used in the Bible, seems to represent a complete period of testing or preparation and, sometimes, cleansing.
Our Lord's temptation for 40 days proved His complete devotion to His Heavenly Father and His opposition to sin as He was about to enter His ministry.
The Israelites' 40-year wandering in the wilderness tested and developed their faith, preparing them to enter the promised land. In addition, during that time, the Hebrews as a people were purged of the unfaithful and disobedient among them. That generation died during the 40 year journey.
There are many instances of 40 as a time period in scripture, and a few of these examples include:
- The rain fell upon the earth 40 days and 40 nights in Noah's day (Genesis 7:12). The flood cleansed the earth of corruption and violence (Genesis 6:11, 12) and prepared it for a new beginning.
- Moses experienced two 40-year time periods which prepared him to be Israel's deliverer. During the first he received his mother's care and guidance before being educated as Pharaoh's grandson (Exodus 2:8-10; Acts 7:21-23, 29).
Afterwards, when he fled Egypt, he spent 40 years in the wilderness of Midian. This second period of comparative isolation allowed him much time for contemplation and refinement of character. And "after forty years had passed, an angel appeared to Moses in the flames of a burning bush in the desert near Mount Sinai." (Acts 7:30) Only then was Moses (both in character and in strength of faith) ready to be used of God to deliver the Israelites from Egyptian bondage.