11 Pass through the host, and command the people, saying, Prepare you victuals; for within three days ye shall pass over this Jordan, to go in to possess the land, which the LORD your God giveth you to possess it.
At the death of Moses, Joshua received the rule; and when the law ended, our true Lord Jesus obtained the rule of the whole world. Therefore, Joshua who typified the Lord said to the people when he came to the Jordan: “Prepare your provisions until the third day.” The third day, dearly beloved, we recognize as the mystery of the Trinity. What food should we prepare so that we may come to the third day? It seems to me that this food should be understood as faith; for Christians it is by faith that they believe in the Trinity and arrive at the sacrament of baptism. Therefore, what Joshua then told his people, the true Joshua or Jesus now tells the Christian people through his ministers. Indeed, what else does this mean: “Prepare your provisions until the third day,” except to receive the mystery of the Trinity? After this the Jordan was crossed just as if the mystery of baptism were completed, and the people of Israel entered the promised land. It is true, brothers; unless a person crosses through the sacrament of baptism, he will not see the land of true promise, that is, eternal beatitude.
For this reason Joshua said to the people, “Prepare your provisions for the journey.” Today, if you willingly listen, Christ our Lord says to you, “If you will follow me, prepare food for the journey.” This food is good works which accompany us like faithful food for the journey to future bliss. Therefore, consider, brothers, that if each one does not prepare food for himself, he cannot follow Joshua when he enters the land of promise.
[AD 542] Caesarius of Arles on Joshua 1:10-11