Racism

 Miriam and Aaron spoke against Moses because of the Cushite woman whom he had married, for he had married a Cushite woman.

Numbers 12:1 ESV

Much of what the Bible has to say about racism is implicit. For example, we're all made in the image and likeness of God, which implies that there's no room for racism. We're all descended from Adam and Eve- it's not like some of us are more evolved than others of us.

Numbers 12 though is explicitly anti-racist. Presumably Moses's first wife Zipporah had died (although polygamy was tolerated at the time). He remarried an African lady, much to the annoyance of His siblings.

I'm not sure of the URL, but I recommend you Google 'John Piper Poem Numbers 12' and hopefully you'll get to a poem he wrote on this incident. Moses's siblings were basically racist, and he had to intercede for them to be forgiven by God. It seems Miriam was the ringleader of the racism, because she was the one who got leprosy as a punishment for her prejudice.

Thankfully, God listened to Moses's intercession for his sister. Interestingly though, when she died, there's no mention of any communal mourning, like there was when Aaron died. It seems her racist attitude marred her legacy as a prophetess of God.

'God, forbid that we would be racist. Please help us to love all peoples equally, and to make Your good news known to all and sundry. In Jesus' name, amen'.