A dictionary of Proverbs (Oxford Paperback Reference)

It’s an ILL bird that fouls its own nest
A condemnation of a person who vilifies his own family, country, etc. Cf. medieval L. nidos commaculans inmundus habebitur ales, the bird is unclean that soils its nest.

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  a 1250 Owl & Nightingale (1960) 1. 99 Dahet habbe [a curse on] that ilke best that fuleth his owe nest. c 1400 N. BOZON Moral Tales (1889) 205 Hyt ys a fowle brydde that fylyth hys owne neste. 1591 H. SMITH Preparative to Marriage 82 It becommeth not any woman to set light by her husband, nor to publish his infirmities for they say, it is an euill bird that defileth his owne nest. 1670 J. RAY English Proverbs 62 It’s an ill bird that beraies its own nest. 1817 SCOTT Rob Roy II. xiii. Where’s the use o’ vilifying ane’s country. .. It’s an ill bird that files its ain nest. 1926 Times 7 Sept. 17 Nothing.. can excuse the bad taste of Samuel Butler ’s virulent attack upon his defenceless family. .. It’s an ill bird that fouls its own nest. 2000 C. GOFF Rant of Ravens i. 2 Miriam cleared her throat. ‘It’s an ill bird that fouls its own nest, dear. If you ask me, it’s about time you dumped him.’ ■ malice
  

ILL gotten goods never thrive
Cf. CICERO PhilippicaII. xxvii. 65 male parta, male dilabuntur, things ill gotten slip away in evil ways. A less colourful saying on the same theme as what is GOT over the Devil’s back is spent under his belly.

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  1519 W. HORMAN Vulgaria 77 Euyll gotten ryches wyll neuer proue longe. c 1577 J . NORTHBROOKE Treatise.. Dicing 95 Euill gotten goods shall neuer prosper. 1609 JONSON Case is Altered V. xii. Ill gotten goods ne’er thriue, I plaid the thiefe, and now am robd my selfe. 1670 J. RAY English Proverbs 98 Ill gotten goods, seldom prosper. 1826 C. LAMB Elia’s Last Essays (1833) ii. That ill-gotten gain never prospers..is the trite consolation administered to the easy dupe, when he has been tricked out of his money or estate. 1937 D. L. SAYERS Busman’s Honeymoon x. Ill gotten goods never thrive. . . Because he hath oppressed and forsaken the poor. ■ action and consequence; retribution