God commanded the people to make flint knives and use them to "circumcise the sons of Israel again, the second time" (5:2). Since it is impossible for one to be circumcised more than once, this obviously refers to the nation as a whole circumcising the second generation of males who had been born in the wilderness and never circumcised as was required (cf. Gen. 17:12).
"And this is the reason why Joshua circumcised them: All the people who came out of Egypt who were males, all the men of war, had died in the wilderness on the way, after they had come out of Egypt. For all the people who came out had been circumcised, but all the people born in the wilderness, on the way as they came out of Egypt, had not been circumcised" (Josh. 5:4,5). With the exception of Joshua, Caleb, some priests, and those who were less than 20 years old at the time of the exodus, all other Hebrew males alive at this time had been born in the wilderness and were all in need of having their foreskins removed in order to obey God (evidently, while wandering in the wilderness they neglected the rite of circumcision). Thus, all males under the age of 40 would need to be circumcised right away. This would have been a monumental undertaking. The pain involved in circumcising an adult male is extreme, and it would have taken great commitment and faith on the part of the people to submit to this order. How so? Because for several days after all the men were circumcised they would be in no condition to defend themselves if attacked by the Canaanites (e.g., Gen. 34:24,25). They would have to rely on God and endure the pain, simply because it was the right thing to do. Friends, sometimes today when we carefully follow the way of the Lord, we will suffer greatly and our only recourse is to wait patiently and rely on God (cf. Matt. 16:24). Do you trust God enough to obey, even when it is going to be painful and perhaps leave you exposed to danger?
"Now the children of Israel camped in Gilgal, and kept the Passover on the fourteenth day of the month at twilight on the plains of Jericho. And they ate of the produce of the land on the day after the Passover, unleavened bread and parched grain, on the very same day. Then the manna ceased on the day after they had eaten the produce of the land; and the children of Israel no longer had manna, but they ate the food of the land of Canaan that year" (Josh. 5:10-12). Several days after the circumcisions, the nation kept the Passover feast. Afterward, they began eating of the food available to them in the bountiful land of Canaan. God had miraculously provided bread from heaven for them for decades, and some of them had eaten manna their entire lives! But that was no longer necessary. The physical resources of the land flowing with milk and honey were more than sufficient to provide for them. God does not continue to use supernatural power to meet a need when natural means become sufficient. Such an observation is quite relevant for the Christian age when considering the cessation of the miraculous gifts of the Holy Spirit toward the beginning of the second century (cf. Mark 16:20; I Cor. 13:8ff; James 1:25). The miraculous gifts continued until God's word was fully revealed and confirmed; then they became unnecessary and ceased, just like the manna in Joshua 5.