A.T. Robertson Commentary Mark 4:39

"And he awoke, and rebuked the wind, and said unto the sea, Peace, be still. And the wind ceased, and there was a great calm." — Mark 4:39 (ASV)

Rebuked the wind (επετιμησεν τω ανεμω) as in Mt 8:26 and Lu 8:24. He spoke to the sea also. All three Gospels speak of the sudden calm (γαληνη) and the rebuke to the disciples for this lack of faith.