A dictionary of Proverbs (Oxford Paperback Reference)

beforehand see PAY beforehand was never well served.
beget see LENGTH begets loathing; LOVE begets love.
Set a BEGGAR on horseback, and he’ll ride to the Devil
A proverb (now frequently used elliptically) with many variations, meaning that one unaccustomed to power or luxury will abuse it or be corrupted by it.

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  1576 G. PETTIE Petit Palace 76 Set a Beggar on horsebacke, and he wyl neuer alight. 1592 NASHE Pierce Penniless 1.174 These whelpes.. drawne vp to the heauen of honor from the dunghill of abiect fortune, haue long been on horseback to come riding to your Diuelship. 1616 T. ADAMS Sacrifice of Thankfulness 6 He that serues the Flesh serues his fellow: And a Beggar mounted on the backe of Honour, rides post to the Diuell. 1669 W. WINSTANLEY New Help to Discourse 151 Set a Beggar on Horse-back, and he will ride to the Devil. 1855 GASKELL North & South I. X. You know the proverb.. ‘Set a beggar on horseback, and he’ll ride to the devil,’—well, some of these early manufacturers did ride to the devil in a magnificent style. 1923 C. WELLS Affair at Flower Acres ii. I should think your early days of forced economy would have taught you not to be quite so extravagant. But there’s an old proverb—’Set a beggar on horse-back —’ and so forth, that jolly well fits you. 1961 W. H. LEWIS Scandalous Regent X. He had a good deal of the vulgarity and insolence of the beggar on horseback. "good fortune; pride
  

beggar see also SUE a beggar and catch a louse; if WISHES were horses, beggars would ride.
BEGGARS can’t be choosers
The substitution of can’t for must not is a recent development. Cf. mid 15th-cent. Fr. qui empruncte ne peult choisir, he who borrows cannot choose.

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  1546 J. HEYWOOD Dialogue of Proverbs I. X. D1 Folke say alwaie, beggers shulde be no choosers. 1728 VANBRUGH Journey to London III. i. My Lords, says I, Beggars must not be Chusers; but some Place about a thousand a Year.. might do pretty weel. 1888 N. J. CLODFELTER Snatched from Poor House iv. Crawl out O’ that bed! I’spose you do feel a little bad, but ‘beggars can’t be choosers!’ 1939 J. SHEARING Blanche Fury 72 ‘I suppose.. you would marry any man with a good character and a fine estate.’..‘Beggars can’t be choosers, you mean!’ 2000 J. ALTMAN Gathering of Spies ix. 150 It would ruin the dress, no doubt about that. But beggars couldn’t be choosers. She drew a breath and then jumped, tucking and rolling as she came out of the train. ■ necessity; poverty
  

begin see CHARITY begins at home; LIFE begins at forty; the LONGEST journey begins with a single step; when THINGS are at the worst they begin to mend; also BEGUN.