But that was just the empty exaggeration and vain threat of a jealous lover. The warning from Christ is intended to be taken literally and exactly. Just listen to yourself. Imagine a tape recorder hung around your neck and picking up every single thing you say. Jesus knew very well about our useless chatter.
Idle words are simply an amusement.
And God's scrutiny of our behavior will be so thorough, according to the Savior, that even these little amusements in our speech will come under the microscope of God's omniscient judgment. Christ is concerned about your every idle word. Answering such questions as these is, for every spiritually sensitive believer, a painful, humbling, and convicting exercise. Only the gracious, powerful, regenerating, and sanctifying work of God can accomplish that.