The number represents testing in human life.
Genesis 7:4 (c) Noah's faith was tested and found to be all that it should be.
Exodus 16:35 (c) GOD's faithfulness was tested and found to be sufficient for all the needs.
Exodus 24:18 (c) Israel's faith and trust were tested and failed. (See Exodus 32:7).
1 Samuel 4:18 (c) Eli was tested. He had judged Israel and failed at the end.
1 Samuel 17:16 (c) Israel was challenged and was proved to be utterly unworthy and cowardly.
Saul reigned forty years and was deposed as a failure.
2 Samuel 5:4 (c) David reigned forty years and ended his rule gloriously.
1 Kings 11:42 (c) Solomon reigned forty years and ended his period of testing in idolatry.
Matthew 4:2 (c) JESUS was tested forty days and forty nights. He came back more than a Conqueror. JESUS revealed Himself to His own for forty days after His resurrection so that they could endure the tests through the years. (See Acts 1:3).