Joshua 7

The hardest part in reading the record of the Israelites as they enter the promised land, is that they just can't seem to follow the constant warnings of the prophets and restrain themselves from the worldly practices and idols of the Canaanites for we read that in the destruction of Jericho -

"...the children of Israel committed a trespass in the accursed thing: for Achan, the son of Carmi, the son of Zabdi, the son of Zerah, of the tribe of Judah, took of the accursed thing: and the anger of the LORD was kindled against the children of Israel."  (Old Testament | Joshua 7:1)

The consequence was that the Lord would not defend them against Ai and many warriors died.  It seems that Achan's family was part of this and the final result Achan confessed -

"Indeed I have sinned against the LORD God of Israel, and thus and thus have I done:
21 When I saw among the spoils a goodly Babylonish garment, and two hundred shekels of silver, and a wedge of gold of fifty shekels weight, then I coveted them, and took them; and, behold, they are hid in the earth in the midst of my tent, and the silver under it.
22 ¶ So Joshua sent messengers, and they ran unto the tent; and, behold, it was hid in his tent, and the silver under it.
23 And they took them out of the midst of the tent, and brought them unto Joshua, and unto all the children of Israel, and laid them out before the LORD.
24 And Joshua, and all Israel with him, took Achan the son of Zerah, and the silver, and the garment, and the wedge of gold, and his sons, and his daughters, and his oxen, and his asses, and his sheep, and his tent, and all that he had: and they brought them unto the valley of Achor.
25 And Joshua said, Why hast thou troubled us? the LORD shall trouble thee this day. And all Israel stoned him with stones, and burned them with fire, after they had stoned them with stones.
26 And they raised over him a great heap of stones unto this day. So the LORD turned from the fierceness of his anger. Wherefore the name of that place was called, The valley of Achor, unto this day."  (Old Testament | Joshua 7:20 - 26)

Alma taught his people -

"...now I say unto you, all you that are desirous to follow the voice of the good shepherd, come ye out from the wicked, and be ye separate, and touch not their unclean things; and behold, their names shall be blotted out, that the names of the wicked shall not be numbered among the names of the righteous, that the word of God may be fulfilled, which saith: The names of the wicked shall not be mingled with the names of my people..."  (Book of Mormon | Alma 5:57)

As we come to Christ, we must leave wickedness touching not he unclean things.  Before Joshua was to pass away, he counsels Israel to continue the work saying -

"I have divided unto you by lot these nations that remain, to be an inheritance for your tribes, from Jordan, with all the nations that I have cut off, even unto the great sea westward.
5 And the LORD your God, he shall expel them from before you, and drive them from out of your sight; and ye shall possess their land, as the LORD your God hath promised unto you.
6 Be ye therefore very courageous to keep and to do all that is written in the book of the law of Moses, that ye turn not aside therefrom to the right hand or to the left;
7 That ye come not among these nations, these that remain among you; neither make mention of the name of their gods, nor cause to swear by them, neither serve them, nor bow yourselves unto them:
8 But cleave unto the LORD your God, as ye have done unto this day."  (Old Testament | Joshua 23:4 - 8)

Remember that these other nations were "ripe in inquity".  As one continues to read the Old Testament, Israel did not completely follow the Lord's instruction, and as a result, wars with neighboring so called nations continued for many years.