Joshua 5:4
And this is the cause why Joshua did circumcise: All the people that came out of Egypt, that were males, even all the men of war, died in the wilderness by the way, after they came out of Egypt.
Cross-reference
In Numbers 14:22, the wilderness generation tested God and died — that rebellion explains why Joshua must circumcise the survivors' sons.
Numbers 26:64 states that none of the first generation census remained, matching the death of all men of war in Joshua 5:4.
Numbers 26:65 explicitly notes that only Caleb and Joshua survived, giving the divine decree behind the fact in Joshua 5:4.
Deuteronomy 2:16 uses identical phrasing 'all the men of war had perished', directly referencing the same event as Joshua 5:4.
1 Corinthians 10:5 recalls the wilderness generation being overthrown, echoing the death of all the fighting men from Egypt in Joshua 5:4.
Hebrews 3:17-19 describes the same wilderness generation who fell due to unbelief, correlating with the death of all men of war in Joshua 5:4.
Genesis 17:10 established circumcision as the covenant sign, which Joshua 5:4 explains was necessary for those born in the wilderness.