“You are taking the wrong sow by the ear.”

Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

Source: Your Best Life Now: 7 Steps to Living at Your Full Potential

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

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

Maxim quoted in a tribute to Cannon on his retirement, reported in The Sun, Baltimore, Maryland (March 4, 1923); Congressional Record (March 4, 1923), vol. 64, p. 5714.

Possibly a misattribution, ascribed to Reade in Notes and Queries (9th Series) vol. 12, 17 October 1903. It appears (as an un-sourced quotation) in Life and Labor (1887) by Samuel Smiles and in the front of The Power of Womanhood by Ellice Hopkins (1899) htm http://www.gutenberg.org/files/13722/13722-h/13722-h..
Apparently a common saying in 19th century. It has been also attributed to an “old Chinese proverb”, Ralph Waldo Emerson (1803-1882), William Makepeace Thackeray (1811–1863), George Dana Boardman (1828-1903), Frances Elizabeth Caroline Willard (1839-1898), James Allen (1864-1912), Marcus Fabius Quintilianus http://en.wikipedia.org/wiki/Quintilian http://www.worldofquotes.com/author/Quintilian-(Marcus-Fabius-Quintilian)/1/index.html and William James.
No original source has ever been isolated. Its structure strongly reflects that of a ""classical Chinese"" set of aphorisms; and it may have been deliberately constructed in that form, by a non-Chinese, to imply an oriental (and, perhaps, far wiser) origin.
Finally, almost all of those who cite the complete piece:
::We sow a thought and reap an act;
::We sow an act and reap a habit;
::We sow a habit and reap a character;
::We sow a character and reap a destiny.
state that, in their view, it was written to expand an embellish the notion that was expressed at Proverbs XXIII:7 (""For as he thinketh in his heart, so is he"").
Attributed

Choruses from The Rock (1934)
Context: The lot of man is ceaseless labor,
Or ceaseless idleness, which is still harder,
Or irregular labour, which is not pleasant.
I have trodden the winepress alone, and I know
That it is hard to be really useful, resigning
The things that men count for happiness, seeking
The good deeds that lead to obscurity, accepting
With equal face those that bring ignominy,
The applause of all or the love of none.
All men are ready to invest their money
But most expect dividends.
I say to you: Make perfect your will.
I say: take no thought of the harvest,
But only of proper sowing.