Do not withhold the sustenance of your wife and children

Khaithama reported:

While we were sitting in the company of 'Abdullah bin 'Umar there came in his steward. He (Ibn 'Umar) said: Have you supplied the provision to the slaves? He said: No. Upon this he said: Go and give (the provision) to them, for the Messenger of Allah (sallallaahu alayhi wa sallam) has said: This sin is enough for a man that he withholds the subsistence from the one whose Quut [food, nourshiment] he owns.

[Sahih Muslim 996]

This incudes your children, wife, khaadim, and others. 

Khaalid bin Uthmaan al-Sabt says regarding the phrase:

"This sin is enough for a man..."

لو لم يكن له من الإثم إلا هذا لكان ذلك كافياً لعظمه

Had he not had any sin except for this one [sin] it would have been sufficient given its magnitude. 

Do not be miserly and earn yourself a major sin.