Smacking the Face (Hadith No. 2232)
Hadith no. 2231 (below) is a repeat. Read it here.
Volume 3, Book 46, Number 733:
Narrated ‘Abdullah bin ‘Umar (radiallaahu `anhu):
That he heard Allah’s Apostle (sallallaahu `alayhi wasallam) saying, “Everyone of you is a guardian and is responsible for his charge; the ruler is a guardian and is responsible for his subjects; the man is a guardian in his family and responsible for his charges; a woman is a guardian of her husband’s house and responsible for her charges; and the servant is a guardian of his master’s property and is responsible for his charge.” I definitely heard the above from the Prophet (sallallaahu `alayhi wasallam) and think that the Prophet (sallallaahu `alayhi wasallam) also said, “A man is a guardian of his father’s property and responsible for his charges; so everyone of you is a guardian and responsible for his charges.”
Volume 3, Book 46, Number 734:
Narrated Abu Huraira (radiallaahu `anhu):
The Prophet (sallallaahu `alayhi wasallam) said, “If somebody fights (or beats somebody) then he should avoid the face.”
Ibn Uthaymeen says about smacking children:
Smacking on the face is risky, because the face is the highest and noblest part of a person and if a person is smacked on the face it is more humiliating and shameful than if he were to be smacked on the back. Hence it is forbidden to smack on the face.
Fataawa Noor ‘ala al-Darb, 13/2
More on smacking children here.