“Life is an echo. What you send out, comes back. What you sow, you reap. What you give, you get. What you see in others, exists in you.”

Song lyrics, The Firstborn Is Dead (1985), Tupelo

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 211.

Saying published anonymously in The Dayspring, Vol. 10 (1881) by the Unitarian Sunday-School Society, and quoted in Life and Labor (1887) by Smiles; this is most often attributed to George Dana Boardman, at least as early as 1884, but also sometimes attributed to William Makepeace Thackeray as early as 1891, probably because in in Life and Labor Smiles adds a quote by Thackeray right after this one, to Charles Reade in 1903, and to William James as early as 1906, because it appears in his Principles of Psychology (1890).
Misattributed
Source: Happy Homes and the Hearts That Make Them

Extensive research of writings by and about Churchill at the Churchill Centre http://www.winstonchurchill.org fails to indicate that Churchill ever spoke or wrote those words.
Some sites list Norman MacEwen as the originator of the quote.
Misattributed
Variant: We make a living by what we get, we make a life by what we give.
Variant: We make a living by what we get. We make a life by what we give.

Reported in Phinneys' Calendar (1878), edited by Andrew Beers.