The noun cruse denotes a small earthenware vessel for liquids. It is of Germanic origin and related to words such as Dutch kroes and Swedish krus, of same meaning.

The expression widow’s cruse signifies an apparently small supply that proves inexhaustible. It is an allusion to the First Book of Kings, 17. The prophet Elijah has been fed by ravens and has drunk from a brook; but because of a drought, the brook has dried up:

(King James Version – 1611)
8 And the word of the LORD came vnto him [= Elijah], saying,
9 Arise, get thee to Zarephath, which belongeth to Zidon, and dwell there: behold, I haue commanded a widow woman there to sustaine thee.
10 So he arose, and went to Zarephath: and when he came to the gate of the citie, behold, the widow woman was there gathering of stickes: and hee called to her, and said, Fetch me, I pray thee, a little water in a vessell, that I may drinke.
11 And as shee was going to fetch it, he called to her, and said, Bring me, I pray thee, a morsell of bread in thine hand.
12 And she said, As the LORD thy God liueth, I haue not a cake, but an handfull of meale in a barrell, and a little oyle in a cruse: and behold, I am gathering two stickes, that I may goe in, and dresse it for me and my sonne, that we may eate it, and die.
13 And Eliiah said vnto her, Feare not, goe, and doe as thou hast said: but make mee thereof a little cake first: and bring it vnto mee, and after make for thee, and for thy sonne.
14 For thus saith the LORD God of Israel, The barrell of meale shall not waste, neither shall the cruse of oyle faile, vntil the day that the LORD sendeth raine vpon the earth.
15 And shee went, and did according to the saying of Eliiah: and she, and he, and her house, did eate many dayes.
16 And the barrell of meale wasted not, neither did the cruse of oyle faile, according to the word of the LORD, which he spake by Eliiah.

The following is from The British Apollo: containing two thousand answers to curious questions in most arts and sciences, serious, comical, and humorous, approved of by many of the most learned and ingenious of both universities, and of the Royal-Society (London – 1726):

Q. I read in Proverbs the 24^th, There is that scattereth, and yet increaseth.
A. The person that scattereth, and yet encreaseth, is the liberal, the charitable man. Such the promises annext to the duty of charity; such the blessings that frequently attend it; that while we give away a portion of our substance, so we do it with prudence and discretion, we enlarge our store. And therefore (tho’ a seeming paradox) division is equivalent to multiplication here, and substraction in contrariety to its nature, becomes addition. If we deal our bread to the hungry, and in imitation of our charitable Lord, bestow, as it were five loaves upon the needy, the fainting multitude, our provisions will encrease by diminution, and the fragments that shall remain to us, will be twelve baskets full. We need no longer to wonder at the widow’s cruse, at her miraculous supply. For the riches of the tender-hearted man, whose bowels of compassion will not suffer him to forget the poor and needy, not only not diminish, but multiply, by his generous donations.

In A Cabinet of Miscellanies (London – 1794), the English author and journalist John Williams (1761-1818), writing under the pseudonym of Anthony Pasquin, denounces

those, who are in the habit of thinking nothing can be good that is not sacerdotal—who, from a miserable impulse of false piety, would tear the bread from the orphan, and purloin the widow’s cruse, to add their mite to the monastic treasury!—who solicit favor with the Deity, through the medium of craft and imposition.

In his column Lines from Lancs [= Lancashire], published in The Stage (London) of 22^nd December 1971, James Hartley wrote:

In Blackpool, St. Annes, and Cleveleys, the emphasis on festive fare has moved to cabaret-style entertainment which has developed tremendously in the clubs, pubs, and guesthouses. All but the humblest of these last are offering their Christmas customers some form of entertainment, much of it “live.”
Busiest man on the Scene and chief provider is Normal Teal with seemingly a widow’s cruse of entertainers. He is personally responsible for laying on quality attractions for dozens of hotels and showbars all along the Nor’west seaboard over the holiday period.

There have been other allusions to the biblical story apart from the expression widow’s cruse. In The Historie of Jonah (around 1653), Zachary Boyd (1585-1653), Church of Scotland minister and university administrator, makes the Lord ask:

(1855 edition)
What say’st thou Jonah? art thou miscontent?
Thy cruse of joye is it already spent,
And nothing left but a displeased mind,
Which is still seeking what it cannot find?

And in The History of Pendennis. His Fortunes and Misfortunes, His Friends and His Greatest Enemy (1849), the British novelist William Makepeace Thackeray (1811-63) wrote:

All this pride and affection of uncle and mother had been trampled down by Pen’s wicked extravagance and idleness! I don’t envy Pen’s feelings (as the phrase is), as he thought of what he had done. He had slept, and the tortoise had won the race. He had marred at its outset what might have been a brilliant career. He had dipped ungenerously into a generous mother’s purse; basely and recklessly spilt her little cruse. O! it was a coward hand that could strike and rob a creature so tender.