But to give one’s advice to others, unasked, is, in effect, to declare that we are much wiser than those to whom we give it; and is a kind of reproaching them with their ignorance and inexperience.

[Il proferire il tuo consiglio non richiesto niuna altra cosa è che un dire di esser più savio di colui cui tu consigli, anzi un rimproverargli il suo poco sapere e la sua ignoranza.]

Giovanni della Casa (1503-1556) Florentine poet, author, diplomat, bishop

Galateo: Or, A Treatise on Politeness and Delicacy of Manners [Il Galateo overo de’ costumi], ch. 18 (1558) [tr. Graves (1774)]
    (Source)

(Source (Italian)). Alternate translations:

To offer advise, unrequested: what is it els but to vaunt youre selfe wiser then he is, whom you do counsell : nay rather it is a plaine checke to him, for his Ignoraunce and folly.
[tr. Peterson (1576)]

To offer your advice unasked, is nothing else than to assert that you are wiser than he to whom you offer it.
[Source (1909)]

To offer your advice without having been asked is nothing else but a way of saying that you are wiser than the man to whom you are giving advice, and even a way of reprimanding him for his limited knowledge and his ignorance.
[tr. Eisenbichler/Bartlett (1986)]