A stitch in time saves nine
A timely effort will prevent more work later.
This is nothing to do with rips in the fabric of the space-time continuum, as some have ingeniously suggested. The meaning of this proverb is often requested at the Phrase Finder Discussion Forum, so I'll be explicit. The question usually asked is "saves nine what"? The 'stitch in time' is simply the sewing up of a small hole or tear in a piece of material, so saving the need for more stitching at a later date when the hole has become larger. Clearly, the first users of this expression were referring to saving nine stitches.
The Anglo Saxon work ethic is being called on here. Many English proverbs encourage immediate effort as superior to putting things off until later; for example, 'one year's seeds, seven year's weeds', 'procrastination is the thief of time' and 'the early bird catches the worm'.
The 'stitch in time' notion has been current in English for a very long time and is first recorded in Thomas Fuller's Gnomologia, Adagies and Proverbs, Wise Sentences and Witty Sayings, Ancient and Modern, Foreign and British, 1732:
"A Stitch in Time May save nine."
Fuller, who recorded a large number of the early proverbs in the language, wrote an explanatory preamble to this one:
"Because verses are easier got by heart, and stick faster in the memory than prose; and because ordinary people use to be much taken with the clinking of syllables; many of our proverbs are so formed, and very often put into false rhymes; as, a stitch in time, may save nine; many a little will make a mickle. This little artiface, I imagine, was contrived purposely to make the sense abide the longer in the memory, by reason of its oddness and archness."
As far as is known, the first person to state unambiguously that 'a stitch in time saves nine', rather than Fuller's less confident 'may save nine', was the English astronomer Francis Baily, in his Journal, written in 1797 and published in 1856 by Augustus De Morgan:
After a little while we acquired a method of keeping her [a boat] in the middle of the stream, by watching the moment she began to vary, and thereby verifying the vulgar proverb, '"A stitch in time saves nine."
See also: the List of Proverbs.