נוֹתֵ֣ן לָ֭רָשׁ אֵ֣ין מַחְס֑וֹר וּמַעְלִ֥ים עֵ֝ינָ֗יו רַב־מְאֵרֽוֹת׃
He that giveth unto the poor shall not lack; But he that hideth his eyes shall have many a curse.
Rashi on Proverbs
will suffer no want (to give him much charity.) And so it is with the teacher who does not withhold Torah from his pupil.