with his hand he stops the tide of evil:
The episode
Henry of Huntingdon tells the story as one of three examples of Canute's "graceful and magnificent" behaviour (outside of his bravery in warfare), the other two being his arrangement of the marriage of his daughter to the later Holy Roman Emperor, and the negotiation of a reduction in tolls on the roads across Gaul to Rome at the imperial coronation of 1027.
In Huntingdon's account, Canute set his throne by the sea shore and commanded the incoming tide to halt and not wet his feet and robes. Yet "continuing to rise as usual [the tide] dashed over his feet and legs without respect to his royal person. Then the king leapt backwards, saying: 'Let all men know how empty and worthless is the power of kings, for there is none worthy of the name, but He whom heaven, earth, and sea obey by eternal laws.'" He then hung his gold crown on a crucifix, and never wore it again "to the honour of God the almighty King".
Later historians repeated the story, most of them adjusting it to have Canute more clearly aware that the tides would not obey him, and staging the scene to rebuke the flattery of his courtiers. There are also earlier parallels in Celtic stories of men who commanded the tides, namely Saint Illtud of Glamorgan, Maelgwn, king of Gwynedd, and Tuirbe, of Tuirbe's Strand in Brittany.