True kindness is a pure divine affinity, Not founded upon human consanguinity.
 Henry David Thoreau, A Week on the Concord and Merrimack Rivers (1849). copy citation

Context

“While we float here, far from that tributary stream on whose banks our Friends and kindred dwell, our thoughts, like the stars, come out of their horizon still; for there circulates a finer blood than Lavoisier has discovered the laws of,—the blood, not of kindred merely, but of kindness, whose pulse still beats at any distance and forever. True kindness is a pure divine affinity, Not founded upon human consanguinity. It is a spirit, not a blood relation, Superior to family and station. After years of vain familiarity, some distant gesture or unconscious behavior, which we remember, speaks to us with more emphasis than the wisest or kindest words.” source