A dictionary of Proverbs (Oxford Paperback Reference)

Because a MAN is born in a stable that does not make him a horse
Sometimes attributed to the Duke of Wellington (1769-1852); see quot. 1969.

• 
  1833 M. SCOTT Tom Cringle’s Log I. iv. ‘I am an Englishman and no traitor, nor will I die the death of one.’.. ‘Truly.. a man does sometimes become a horse by being born in a stable.’ 1906 Times Literary Supplement 27 Apr. 147 Except on the principle that the man who is born in a stable is a horse, [he] was not an Irishman at all. 1969 E. LONGFORD Wellington: Years of Sword viii. If Wellington was ever chaffed for being an Irishman and replied with a notorious quip, it was probably during this period [1807]: Because a man is born in a stable that does not make him a horse. 1980 J. O’FAOLAIN No Country for Young Men ii. Father Casey.. has a theory that the Irish back in Ireland have less claim to Irishness than men like himself. Something to do with.. being born in a stable not necessarily making you a horse. "human nature; origins
  

man see also BETTER be an old man’s darling, than a young man’s slave; a BLIND man’s wife needs no paint; never send a BOY to do a man’s job; the CHILD is father of the man; CLOTHES make the man; in the COUNTRY of the blind, the one-eyed man is king; DO right and fear no man; a DROWNING man will clutch at a straw; the EARLY man never borrows from the late man; every ELM has its man; EVERY man for himself; EVERY man for himself, and devil take the hindmost; EVERY man for himself, and God for us all; EVERY man has his price; EVERY man is the architect of his own fortune; EVERY man to his taste; EVERY man to his trade; it’s ill speaking between a FULL man and a fasting; a HUNGRY man is an angry man; you should KNOW a man seven years before you stir his fire; a man who is his own LAWYER has a fool for his client; one man’s LOSS is another man’s gain; MANNERS maketh man; like MASTER, like man; one man’s MEAT is another man’s poison; MONEY makes a man; a MONEYLESS man goes fast through the market; NEEDLES and pins,.. when a man marries, his trouble begins; NINE tailors make a man; NO man can serve two masters; NO man is a hero to his own valet; NO moon, no man; there is NOTHING so good for the inside of a man as the outside of a horse; the RICH man has his ice in the summer and the poor man gets his in the winter; give a man ROPE enough and he will hang himself; SIX hours’ sleep for a man, seven for a woman, and eight for a fool; one man may STEAL a horse, while another may not look over a hedge; the STYLE is the man; TIME and tide wait for no man; man fears TIME, but time fears the pyramids; for WANT of a nail the shoe was lost; the WAY to a man’s heart is through his stomach; a WILFUL man must have his way; when the WIND is in the east, ‘tis neither good for man nor beast; a WOMAN without a man is like a fish without a bicycle; a YOUNG man married is a young man marred; also MEN.