The Noble Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have mercy upon him) stated:

It is befitting for the man if he is one who is afflicted with (the committing of) an act of disobedience from the acts of disobedience that he is diligent upon not letting his family witness him committing it. I’ll give an example for that in the matter of smoking.  Some of the people are afflicted with this act of disobedience.  Then the person smokes in front of his children and as a result of that they become accustomed to this and possibly smoke as their father smokes.  With that, he (the father) becomes one who has directed (his children) to an evil so upon him is the act of sin and the sin of those who acted upon it (due to him) until the Day of Judgment.

Source: Ahkaam min al-Quraan al-Kareem 1/481

Translated by Abu Yusuf Khaleefah
29th of Muharram, 1437 (11-11-2015)
Masjid Nur Allah, Queens, NYC