действовать исподтишка
From LSJ
κόραξ δ' ἐπαίνῳ καρδίην ἐχαυνώθη → the flattered crow was filled with pride, the flattered crow became elate in heart
κόραξ δ' ἐπαίνῳ καρδίην ἐχαυνώθη → the flattered crow was filled with pride, the flattered crow became elate in heart