Miriam and Aaron talked against Moses behind his back because of his Cushite wife (he had married a Cushite woman).
They said, "Is it only through Moses that God speaks? Doesn't he also speak through us?" God overheard their talk.
Now the man Moses was a quietly humble man, more so than anyone living on Earth.
God broke in suddenly on Moses and Aaron and Miriam saying, "Come out, you three, to the Tent of Meeting." The three went out.
God descended in a Pillar of Cloud and stood at the entrance to the Tent. He called Aaron and Miriam to him. When they stepped out,
he said, Listen carefully to what I'm telling you. If there is a prophet of God among you, I make myself known to him in visions, I speak to him in dreams.
But I don't do it that way with my servant Moses; he has the run of my entire house;
I speak to him intimately, in person, in plain talk without riddles: He ponders the very form of God. So why did you show no reverence or respect in speaking against my servant, against Moses?
The anger of God blazed out against them. And then he left.
When the Cloud moved off from the Tent, oh! Miriam had turned leprous, her skin like snow. Aaron took one look at Miriam - a leper!
He said to Moses, "Please, my master, please don't come down so hard on us for this foolish and thoughtless sin.
Please don't make her like a stillborn baby coming out of its mother's womb with half its body decomposed."
And Moses prayed to God: Please, God, heal her, please heal her.
God answered Moses, "If her father had spat in her face, wouldn't she be ostracized for seven days? Quarantine her outside the camp for seven days. Then she can be readmitted to the camp."
So Miriam was in quarantine outside the camp for seven days. The people didn't march on until she was readmitted.
Only then did the people march from Hazeroth and set up camp in the Wilderness of Paran.