Brevity is the mark of the skilful proverb, brevity and yet profundity: the ability to express in few words what gets to the essence of a matter. To understand this comparison we should as usual consider carefully the distinctive features of the illustration.
Repentance involves the breaking of the hinges of the old life in order that our souls may move in a new way and turn to Jesus Christ for life. No one should think therefore that small incremental changes can get him into the kingdom of heaven, for the change required is revolutionary. God does not keep the old sinful ways and adapt them to his purpose, but all things must be made new by a radical new creation.