In King Lear, Act II, Scene 4, the Fool says to Lear
Fathers that wear rags
Do make their children blind;
But fathers that bear bags
Shall see their children kind.
This statement follows Lear's discovery that Goneril and Regan have detained and publicly humiliated his emissary, Kent. He can't believe they would disrespect him this way. The Fool tries to enlighten him.
Lear has decided to give his three daughters their inheritance before he dies. By giving away his kingdom, he has left himself with nothing. To "wear rags" is here a metaphor for poverty. Because his children now have what they want, they can ignore him, or are figuratively not seeing him or "blind."
Fathers with "bags," that is bags of money, or who are wealthy, instead give their children reasons to be "kind." They must continue to treat their father well in hopes of inheriting one day.
Lear, the Fool continues, can expect a lot of pain and sorrow, "dolours," from his daughters--so many pains that it would take a year to tell them all.