And G‑d spoke suddenly to Moses, Aaron and Miriam…And He called to Aaron and Miriam… If there be a prophet among you, I G‑d make Myself known to him in a vision, and speak to him in a dream. Not so is it with Moses my servant… Face to face I speak with him. (12:4-8)

G‑d appeared to them suddenly. Aaron and Miriam began to call "Water! Water!" for they needed to purify themselves and were caught unprepared. G‑d wished to demonstrate to them the difference between their prophecy and the prophecy of Moses: with Moses, there was no set time to speak, for the Divine presence was to be found with him at all times.

- Rashi's commentary

For several days in 1804 the small town of Zhlobin hosted an encounter of two great chassidic groups. The occasion was the famous "Zhlobener wedding" in which a granddaughter of Rabbi Schneur Zalman of Liadi wed a grandson of Rabbi Levi Yitzchak of Barditchov. During the festivities, chassidim of both Rebbes hopped from event to event, comparing notes as to what was happening in "Chabad" or 'Barditchov'"

At one point, Rabbi Schneur Zalman asked: "What's going on at the mechuton's?"1 The chassidim informed him that Rabbi Levi Yitzchak had already finished with the morning prayers. "What a mechuton!" remarked the Rebbe. "He runs a hand over his eyes, and his soul is ready to soar in prayer. I could never manage such a feat — I cannot even begin to pray without several hours of preparation."

Later in the day, Rabbi Levi Yitzchak inquired after Rabbi Schneur Zalman and was told that the latter was still before his morning prayers. "What a mechuton!" said the Barditchover. "Whenever he arrives, he is accepted with open arms. As for myself, if I wish to enter the heavenly gates of prayer I must come at the appointed hour, when the door is open for all…"