Source: Originally Frederick William Faber, sermon “On Kindness in General”, found in Spiritual Conferences, a collection of his oratory, ca. 1860.

Original Quote: No kind action ever stops with itself. One kind action leads to another. Good example is followed. A single act of kindness throws out roots in all directions, and the roots spring up and make new trees. The greatest work that kindness does to others is that it makes them kind themselves.

Note: Often misattributed to Amelia Earhart, as the same wording found in books published before her birth.