According to Moses, this verse is about two groups of people planning to share their families and live together as friends, so they can become like one big family. They are saying they will let their daughters marry each other's sons to make this happen.
Genesis 34:16: Then will we give our daughters unto you, and we will take your daughters to us, and we will dwell with you, and we will become one people.
This verse advises not to be "unequally yoked with unbelievers," contrasting with the open agreement for intermarriage with Shechem.
2 Corinthians 6:14: Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?