Joshua 23&24 - Joshua tells them that they are not to act like the rest of the world around them.

Josh 23:5
"And the LORD your God, He shall thrust them out from before you and drive them from before you; and you shall possess their land, just as the LORD your God promised you.
Josh 23:6
"Be very firm, then, to keep and do all that is written in the book of the law of Moses, so that you may not turn aside from it to the right hand or to the left,

Joshua is telling the people that they are to do ALL that is written in the Law of Moses (Deut. 5:32-33, 12:32, 28:14, Prov. 4:26-27, Isa. 1:16-18). Do not turn to the right or to the left. Why did John the Baptist come (Matt. 3:1-3)?
Josh 23:7
in order that you may not associate with these nations, these which remain among you, or mention the name of their gods, or make anyone swear by them, or serve them, or bow down to them.
Josh 23:8
"But you are to cling to the LORD your God, as you have done to this day.

Joshua told the people to hold fast, or cling, to Yahweh. That obviously means to obey Him and keep His Word. Peter told the Gentiles to do the same thing in the Book of Acts Acts 11:23).
Josh 23:9
"For the LORD has driven out great and strong nations from before you; and as for you, no man has stood before you to this day.

Josh 23:10
"One of your men puts to flight a thousand, for the LORD your God is He who fights for you, just as He promised you.
Josh 23:11
"So take diligent heed to yourselves to love the LORD your God.

To love Yahweh our Elohim is of the utmost importance (Ex. 20:4-6, Romans 8:28).
Josh 23:12
"For if you ever go back and cling to the rest of these nations, these which remain among you, and intermarry with them, so that you associate with them and they with you,
Josh 23:13
know with certainty that the LORD your God will not continue to drive these nations out from before you; but they shall be a snare and a trap to you, and a whip on your sides and thorns in your eyes, until you perish from off this good land which the LORD your God has given you.

Joshua tells them that they are not to act like the rest of the world around them. We are told as followers of Messiah not to be like the world 1 John 2:16-17).