Is one obligated to fulfill a parental command given in childhood after reaching adulthood?

If the child knows that what his parents asked of him in his youth is still required now, then he must obey them if the request is for something permissible (maʿruf). However, if they commanded him to do something while he was not yet an adult, and then he reached adulthood, he is not obliged to do it, though it is preferable to hasten to fulfill what they desire. Defining what requires obedience to parents and what does not is a difficult matter.