This is the 60th fable to be found in Roger L'Estrange's Fables and Storyes Moralized. Being a Second Part of The Fables of Aesop and Other Eminent Mythologists, &c, London, Printed for R. Sare at Grayes-Inn-gate in Holbourn, 1699, page 53.
Here is Roger L'Estrange's text, with spelling and other idiosyncrasies in tact:
The Dog who was Afraid of the Rain
IT was observ’d in a Family with all Sorts of Dogs in’t, that one Curr among the rest would never be gotten out of the House in Rainy Weather. His Fellows took Notice of it; and would never let him be quiet till he told them the Meaning on’t: which, in short was This: I was terribly scalt once, a great while ago, and I have been afraid of Water, says he, ever since. His Companions told him he talk’d like a Fool, for Rain-water was Cold, and there could be no Danger in it. Well well! Says he, let it be Hot, or let it be Cold, ’tis Water still; and how shall I know whether it be the one or the other, till I feel it? And by That time, it will be too late to prevent the Mischief.
Moral: It is folly to fear something without a proper cause but it is wise to be wary when there is reasonable ground for it.
Text: Roger L’Estrange (2/60, 1699).