Rashi on Numbers 12:15/רש"י על במדבר י״ב:ט״ו

1והעם לא נסע AND THE PEOPLE JOURNEYED NOT [TILL MIRIAM WAS BROUGHT IN] — This honour the Omnipresent showed her as a reward for the single hour she tarried for Moses’ sake when he was thrown into the river, as it is said, (Exodus 2:4) “And his sister placed herself afar off (i. e. she waited) [to know what would be done to him]” (Sotah 9b).