So Joshua made peace with them, and made a covenant with them to let them live; and the rulers of the congregation swore to them."
Joshua 9:14-15 (NKJV)
In my family, sometimes when giving Christmas gifts, someone buys a gift, but rather than leave the gift in the box that it came in, the person puts the gift into another box. So, when the person receiving the gift takes off the wrapping paper, they see the outside of a box that may not actually represent what is inside. Everyone in my family knows that they have to open the box to see what is really inside of it. No matter what the package looks like on the outside, it does not tell you what is really on the inside.
Before Israel entered the Promised Land, God cautioned them about the people who were living there, because those people worshiped false gods, and even sacrificed their children to their false gods. But there was one group of people that fooled the leaders of Israel. The people of Gibeon came pretending to be from a distant land. Rather than finding out what God had to say about those people, Israel looked at what the people had and made a covenant with them; this was a mistake that caused Israel problems.
Too many people today look at the outside of something, the packaging, or the style of a thing and accept it on that basis, rather than checking into it and finding out what is really inside and, more importantly, seeing what God has to say about it. We should never value the style or look of something over the actual content or quality of the thing. We need to listen to God's direction and use the godly principles we find in God's Word to determine if something is really acceptable or not, instead of just accepting something at face value.