Man is never less sincere than when he asks, or offers, advice. When he asks it, he seems to defer to the wisdom of his friend, but really he seeks approval of his own opinion, and to make his friend responsible with him for his actions. When he offers advice, he seems to repay the confidence of his inquirer with disinterested zeal, while really seeking to bolster his own advantage or reputation.
Duc de La Rochefoucauld (1613 - 1680)
Source: Réflexions ou Sentences et Maximes Morales
Nothing is less sincere than our mode of asking and giving advice. He who asks seems to have a deference for the opinion of his friend, while he only aims to get approval of his own and make his friend responsible for his action. And he who gives advice repays the confidence supposed to be placed in him by a seemingly disinterested zeal, while he seldom means anything by his advice but his own interest or reputation.