ἐπικουρεῖν

From LSJ

ὁ γὰρ μανθάνων κιθαρίζειν κιθαρίζων μανθάνει κιθαρίζειν → he who is learning the harp, learns the harp by harping

Source

Lexicon Thucydideum

auxilio venire, to come to aid, 1.49.7, 5.23.3, 7.57.10.