Rod puzzle

Proverb 22:15 Foolishness is bound up in the heart of a child, but the rod of correction shall drive it far from him.

Proverb 13:24 He that spareth his rod hateth his son: but he that loveth him chasteneth him

But:

Psalm 23:4 thy rod and thy staff they comfort me.

Why is the rod a comfort? I do know that children do well with firm boundries. They don't always like them, but they thrive within them. A rod can be used to get the dumb sheep's attention, or to whack it back in line with the others, or, I suppose, to injure it. Discipline is to get our attention and help us see the right way to go. If the only result of it is injury, then anger is the most likely response. Anger causes rebellion. The rod, or indeed any discipline, must be used in such a way as to gain attention, but not create anger. More on this topic later.