'Foolishly' in the Bible

And Samuel said to Saul, Thou hast done foolishly: thou hast not kept the commandment of the LORD thy God, which he commanded thee: for now would the LORD have established thy kingdom upon Israel for ever.

Then Saul said, "I've wronged you. Return, my son David, for I won't harm you again because my life was precious to you today. Look, I've acted foolishly and have made a very great mistake."