“At present I shall only give you my Opinion that tho’ your Reasonings are subtle, and may prevail with some Readers, you will not succeed so as to change the general Sentiments of Mankind on that Subject, and the Consequence of printing this Piece will be a great deal of Odium drawn upon your self, Mischief to you and no Benefit to others. He that spits against the Wind, spits in his own Face.”

Letter to unknown recipient (13 December 1757) http://teachingamericanhistory.org/library/index.asp?document=473. The letter was published as early as 1817 (William Temple Franklin, The Works of Benjamin Franklin, volume VI, pp. 243-244). In 1833 William Wisner ("Don't Unchain the Tiger," American Tract Society, 1833) identified the recipient as probably Thomas Paine, which was echoed by Jared Sparks in his 1840 edition of Franklin's works (volume x, p. 281). (Presumably it would have been directed against The Age of Reason, his deistic work which criticized orthodox Christianity.) Calvin Blanchard responded to Wisner's tract in The Life of Thomas Paine (1860), pp. 73-74, by noting that Franklin died in 1790, while Paine did not begin writing The Age of Reason until 1793, and incorrectly concluded that the letter did not exist. Paul F. Boller, Jr., and John George, included it in They Never Said It: A Book of Fake Quotes, Misquotes, & Misleading Attributions (1989), on p. 28. Moncure Daniel Conway pointed out (The Life of Thomas Paine, 1892, vol I, p. vii) that the recipient could not be Thomas Paine, in that he, unlike Paine, denied a "particular providence". The intended recipient remains unidentified.
Parts of the above have also been rearranged and paraphrased:
I would advise you not to attempt Unchaining The Tiger, but to burn this piece before it is seen by any other person.
If men are so wicked with religion, what would they be if without it?
If men are so wicked with religion, what would they be Without it? Think how many inconsiderate and inexperienced youth of both sexes there are, who have need of the motives of religion to restrain them from vice, to support their virtue, and retain them in the practice of it till it becomes habitual.
Epistles
Context: I have read your Manuscript with some Attention. By the Arguments it contains against the Doctrine of a particular Providence, tho’ you allow a general Providence, you strike at the Foundation of all Religion: For without the Belief of a Providence that takes Cognizance of, guards and guides and may favour particular Persons, there is no Motive to Worship a Deity, to fear its Displeasure, or to pray for its Protection. I will not enter into any Discussion of your Principles, tho’ you seem to desire it; At present I shall only give you my Opinion that tho’ your Reasonings are subtle, and may prevail with some Readers, you will not succeed so as to change the general Sentiments of Mankind on that Subject, and the Consequence of printing this Piece will be a great deal of Odium drawn upon your self, Mischief to you and no Benefit to others. He that spits against the Wind, spits in his own Face. But were you to succeed, do you imagine any Good would be done by it? You yourself may find it easy to live a virtuous Life without the Assistance afforded by Religion; you having a clear Perception of the Advantages of Virtue and the Disadvantages of Vice, and possessing a Strength of Resolution sufficient to enable you to resist common Temptations. But think how great a Proportion of Mankind consists of weak and ignorant Men and Women, and of inexperienc’d and inconsiderate Youth of both Sexes, who have need of the Motives of Religion to restrain them from Vice, to support their Virtue, and retain them in the Practice of it till it becomes habitual, which is the great Point for its Security; And perhaps you are indebted to her originally that is to your Religious Education, for the Habits of Virtue upon which you now justly value yourself. You might easily display your excellent Talents of reasoning on a less hazardous Subject, and thereby obtain Rank with our most distinguish’d Authors. For among us, it is not necessary, as among the Hottentots that a Youth to be receiv’d into the Company of Men, should prove his Manhood by beating his Mother. I would advise you therefore not to attempt unchaining the Tyger, but to burn this Piece before it is seen by any other Person, whereby you will save yourself a great deal of Mortification from the Enemies it may raise against you, and perhaps a good deal of Regret and Repentance. If Men are so wicked as we now see them with Religion what would they be if without it?