I’d say this phrase is not Albert Einstein or Stephen Hawking philosophizing on time warps, but is just a very old metaphorical proverb – one of those sayings which can’t be ascribed to any one person in particular. It’s probably just the collective wisdom of mankind, which is what a lot of proverbs (aphorisms, homilies, etc.) are. It alludes to fixing a problem when you first see it so that you wont have to waste more time fixing it later when it gets worse – repair now, save later – one stitch now will save you nine later.
To make this kosher, though, I have to give what official etymology I could find (for what it’s worth – which ain’t much).
Random House Dictionary of America’s Popular Proverbs and Saying:
A stitch in time saves nine. If you deal with problems immediately, when they first appear, you will save yourself a lot of money and trouble after. This adage is listed in the 1732 Thomas Fuller's book of proverbs, and was first cited in the United States in the 1787 'Journal of Tour of North America in 1796-1791' by Francis Bally (1774-1844). The word 'nine' was introduced for assonance [[vowel rhyming]].
Ken G (Fort Collins, CO, USA) – 10/12/02
Submitted by Ken Greenwald (Fort Collins, CO - U.S.A.)