This quote is uttered by Mr. Bennet and occurs in the second chapter, as part of a discussion between the Bennets about the new exciting ingredient that has been injected into their community in the form of Mr. Bingham. The novel begins of course with this news and the insistence of Mrs. Bennet that Mr. Bennet must make Mr. Bingham's acquaintance so that "he may fall in love" with one of their daughters. Mr. Bennet, who delights in vexing his wife, refuses overtly but then is one of the first to pay his respects to Mr. Bingham. The quote you have identified comes as he reveals this to his wife and children. Note what he says:
A fortnight's acquaintance is certianly very little. One cannot know what a man really is by the end of a fortnight. But if we do not venture, somebody else will; and after all, Mrs. Long and her nieces must stand their chance; and therefore, as she will think it an act of kindness, if you decline the office, I will take it on myself.
Note how Mr. Bennet mocks his wife, talking of giving other women "the chance" to ensnare Mr. Bingham and also indirectly criticising Mrs. Bennet's willingness to marry any of her daughters off to Mr. Bingham without even getting to know him.