“And Joshua said unto the people, Sanctify yourselves: for to morrow the LORD will do wonders among you.” (Joshua 3:5 KJV)
Sanctify? As in to clean, consecrate, hallow, or dedicate? Why sanctify? What does sanctification do for you? It may signify a proper fit. If you are attending a black tie formal event, you clean up and grab a nice suit out of your closet (or rent one). If you are going to do some serious repair to your car, you may slip into a comfortable pair of overalls that you do not mind getting dirty. There is a certain fitness for the event you wish to participate in. That is not to say that you cannot attend the black tie event in your overalls nor that you cannot repair your car in a tuxedo. You may feel very out of place doing so though.
There is a great deal more to this command to sanctify than merely changing your garments. The law that Moses gave was still freshly ringing in their ears. They likely knew better then than we do now what God expected of a sanctified individual. Would they be able to get that clean in the time they had before crossing the Jordan river? Would they be able to get that clean at all? Even Joshua who would have had the best opportunity to spend the most time in dedication shows no sign of it in the coming verses. This is not to say that no attempt was made. I am sure many of the population did what they could and did just what was asked of them in sanctifying the best that they could.
Notice two important things about this request. First, a complete sanctification was not dependent on God doing what He planned to do. Someone in the crowd who may have completely disregarded the command, did not prevent the great wonder from being done. God's grace in a truly unmerited fashion was willing to move forward whether or not the individual was capable of a total and complete self sanctification. Second, those who did not even make the attempt were probably the least able to see what God was actually doing.
To the casual observer, the water was stopped up, they crossed, and after they got to the other side the water returned. If they did not stub their toe or twist their ankle in the process; they may not have seen much else. To the one interested in setting their hearts and minds on God and cleansing their body along with everything in their possession; it may have looked quite different. They may have noticed the extra twelve stones being brought from the river bed, where they were placed, and what they signified. They may have noticed the place where the water stopped (Adam) and where it remained dry to (the dead sea) and what that meant. They were likely the ones given the most courage because they cleaned their hearts of themselves and waited for the greatness of God's wonders.
Often to sanctify is more than to clean, consecrate, hallow, or dedicate. It is to put aside what you think is filling you that you may be able to be filled.
“But sanctify the Lord God in your hearts: and be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear: (1 Peter 3:15 KJV)