Confucius. Book 1, Chapter 11.
Book 1, Hsio R.
The Master said, "While a man's father is alive, look at the bent of his will; when his father is dead, look at his conduct. If for three years he does not alter from the way of his father, he may be called filial."
Text source: Lun Yu, The Confucian Analects. Translated by James Legge.