Kindness is a language the dumb can speak and the deaf can hear and understand.
Christian Nestell Bovee (1820-1904) American epigrammatist, writer, publisher
Thoughts, Feelings, & Fancies (1857)
Slightly revised in Bovee's Intuitions & Summaries of Thought (1862): "Kindness: a language which the dumb can speak, and the deaf can understand."
Since the 2000s, frequently misattributed to Mark Twain. More information: The Apocryphal Twain: "Kindness is language the deaf can hear." - Center for Mark Twain Studies.