William Burkitt on Colossians 3:21

Here the parents duty, that is the duty of both parents, is laid down, provoke not your children to wrath; that is, abuse not your power and authority over them, by being too severe unto them; imbitter not their spirits against you, by denying them what is convenient for them, by inveighing with bitter words against them, by unjust, unseasonable, or immoderate correcting of them; give them no just occasion to be angry.

The reason is added, lest they be discouraged; either dispirited and heartless, or desperate and hardened; lest by dejection of spirit, they become stupid. A parent's conduct must be moderated with prudence, shunning the extremes of too much indulgence on the one hand, and too great rigour and severity on the other.