Laudator Temporis Acti

Euripides, fragment 508 (tr. Christopher Collard and Martin Cropp):

It is an old saying: the young are strong in action, but the old are strong in counsel.

παλαιὸς αἶνος· ἔργα μὲν νεωτέρων,
βουλαὶ δ' ἔχουσι τῶν γεραιτέρων κράτος.

Homer, Iliad 4.318-325 (Nestor speaking; tr. A.T. Murray):

Son of Atreus, verily I myself could wish that I were such a one as on the day when I slew goodly Ereuthalion. But in no wise do the gods grant to men all things at one time. As I was then a youth, so now doth old age attend me. Yet even so will I abide among the charioteers and urge them on by counsel and by words; for that is the office of elders. Spears shall the young men wield who are more youthful than I and have confidence in their strength.

Ἀτρεΐδη, μάλα μέν τοι ἐγὼν ἐθέλοιμι καὶ αὐτὸς
ὣς ἔμεν ὡς ὅτε δῖον Ἐρευθαλίωνα κατέκταν.
ἀλλ᾽ οὔ πως ἅμα πάντα θεοὶ δόσαν ἀνθρώποισιν·
εἰ τότε κοῦρος ἔα νῦν αὖτέ με γῆρας ὀπάζει.
ἀλλὰ καὶ ὣ ἱππεῦσι μετέσσομαι ἠδὲ κελεύσω
βουλῇ καὶ μύθοισι· τὸ γὰρ γέρας ἐστὶ γερόντων.
αἰχμὰς δ᾽ αἰχμάσσουσι νεώτεροι, οἵ περ ἐμεῖο
ὁπλότεροι γεγάασι πεποίθασίν τε βίηφιν.

Euripides, fragment 291 (tr. Christopher Collard and Martin Cropp):

My son, young men's hands are eager for action, true, but the judgement of their elders is better; for time's teaching is the most subtle.

ὦ παῖ, νέων τοι δρᾶν μὲν ἔντονοι χέρες,
γνῶμαι δ' ἀμείνους εἰσὶ τῶν γεραιτέρων·
ὁ γὰρ χρόνος δίδαγμα ποικιλώτατον.

Euripides, fragment 619 (tr. Christopher Collard and Martin Cropp):

Old age, my son, is wiser, and safer, than younger heads, and experience overcomes inexperience.

τὸ γῆρας, ὦ παῖ, τῶν νεωτέρων φρενῶν
σοφώτερον πέφυκε κἀσφαλέστερον,
ἐμπειρία τε τῆς ἀπειρίας κρατεῖ.

Quintus Smyrnaeus 5.152-156 (Nestor speaking; tr. Frederick M. Combellack):

I suggest to you that you listen to me; I'm a great deal older than you, not just a little, and, besides my advanced years, I'm a sensible man. I've been through a lot, good and painful both. In making plans, a well-informed old man is better than a younger one, because of his vast knowledge.

ἀλλ᾽ ἄγ᾽ ἐμοὶ πείθεσθον, ἐπεί ῥα γεραίτερός εἰμι
λίην, οὐκ ὀλίγον περ, ἔχω δ᾽ ἐπὶ γήραϊ πολλῷ
καὶ νόον, οὕνεκεν ἐσθλὰ καὶ ἄλγεα πολλὰ μόγησα·
αἰεὶ δ᾽ ἐν βουλῇσι γέρων πολύϊδρις ἀμείνων
ὁπλοτέρου πέλει ἀνδρός, ἐπεὶ μάλα μυρία οἶδε.

Cf. Renzo Tosi, Dictionnaire des sentences latines et grecques, tr. Rebecca Lenoir (Grenoble: Jérôme Millon, 2010), #1081, pp. 795-796.

For a different point of view see Henry David Thoreau (1817-1862), Walden, chapter 1:

Age is no better, hardly so well, qualified for an instructor as youth, for it has not profited so much as it has lost. One may almost doubt if the wisest man has learned anything of absolute value by living. Practically, the old have no very important advice to give the young, their own experience has been so partial, and their lives have been such miserable failures, for private reasons, as they must believe; and it may be that they have some faith left which belies that experience, and they are only less young than they were. I have lived some thirty years on this planet, and I have yet to hear the first syllable of valuable or even earnest advice from my seniors. They have told me nothing, and probably cannot tell me anything, to the purpose.