It’s not by Socrates, but it was in a book

The tale of the 3 sieves as told by Socrates has saturated the internet. Sadly, it is not a Socrates story and may have roots in a Protestant missionary in India in the 1800s. But it did appear in a book:

“But perhaps we ought to think of the three sieves, before we allow ourselves to speak of others,” observed the Bishop.

“And what is that story?” said Mr. Arden.

“It is not a story!” he replied, “but a maxim, which all will do well to attend to when they speak of those that are absent. The maxim is this, that before we allow ourselves to find fault with any one behind his back, we should ask ourselves three questions. The first, ‘Is it true?’ The second, ‘Is it kind?’ The third, ‘Is it necessary?’”

Rev. Charles B. Tayler, Lady Mary or Not of the World (London, 1845, p. 205)