Scholiast on Sophocles, Oedipus at Colonus
954 = Suda
Θ 574 (tr. David A. Campbell):
This is also a proverb, 'anger is the last of a man to grow old', applied to older men, since the older they are, the stronger their anger. Alcaeus [fragment 442] mentions it as being of general application.
τοῦτο δὲ καὶ παροιμιακῶς λέγεται, ὅτι ὁ θυμὸς ἔσχατον γηράσκει. λέγεται δὲ διὰ τοὺς πρεσβυτέρους. ὅσῳ γὰρ γηράσκουσι τὸν θυμὸν ἐρρωμενέστερον ἔχουσι. καὶ Ἀλκαῖος ὡς λεγομένου κατὰ τὸ κοινὸν αὐτοῦ μιμνήσκεται.
I vii 13) translates the proverb as "Ira omnium tardissime senescit."