Early uses of the proverb refer specifically to women.
When love once pleads admission to our hearts‥The woman that deliberates is lost.
[1713 Addison Cato iv. i.]
It has often been said of woman that she who doubts is lost‥never thinking whether or no there be any truth in the proverb.
[1865 Trollope Can You forgive Her? ii. x.]
In Utah it is emphatically true, that he who hesitates is lost—to Mormonism.
[1878 J. H. Beadle Western Wilds xxi.]
Dolly hesitated, and with the proverbial result.
[1887 Blackmore Springhaven xlii.]
‘Sometimes he who hesitates is lost‥and ends up several miles from the next freeway exit.’
[2001 Washington Times 8 Nov. D6 (Herb & Jamaal comic strip)]
Related to: decision and indecision
Bibliography of major proverb collections and works cited from modern editions is available here.
One who cannot come to a decision will suffer for it, as in I couldn't make up my mind, and now the offer has expired--he who hesitates is lost. Although the idea is undoubtedly older, the present wording is a misquotation or an adaptation from Joseph Addison's play Cato
(1712): "The woman that deliberates is lost."