Rashi on Numbers 12:4/רש"י על במדבר י״ב:ד׳

1פתאם SUDDENLY — He revealed himself to them suddenly just when they were unclean as a result of marital intercourse, so that they cried; “Water, water!” (for purification). He did this to give them to understand that Moses had acted rightly in that he had separated from his wife, since the Shechinah used to reveal Itself to him at all times and there was no definite time fixed for the Divine communication (Midrash Tanchuma, Tzav 13).

2צאו שלשתכם GO OUT YOU THREE [UNTO THE APPOINTED TENT] — This tells us that the names of all three of them were mentioned as one utterance, something that is impossible for a human mouth to articulate and a human ear to catch (Sifrei Bamidbar 102).