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"").