The Bible is not always explicit on social issues except when it is. In Numbers chapter 12, the scripture is very explicit on the sin of racism. God doesn’t take it lightly, especially when it’s used to thwart His sovereign grace. Miriam and Aaron learned that lesson the hard way.
Miriam and Aaron spoke against Moses because of the Cushite woman whom he had married, for he had married a Cushite woman. And they said, “Has the LORD indeed spoken only through Moses? Has he not spoken through us also?” And the LORD heard it. Now the man Moses was very meek, more than all people who were on the face of the earth. (Numbers 12: 1-2)