Hitting or Spanking one’s children-Part 1-The allowance and age:
Small children: It is permitted for one to hit his small children for disciplinary measures. This applies even to [non-biological] children that are part of one’s household, such as an [adopted] orphan [or foster child].
Adult children? It is forbidden for one to hit his adult children [whether male or female, due to fear that this may cause them to retaliate and transgress the command to honor and fear one’s parents]. One who hit his adult children would be placed in excommunication as he transgresses the prohibition of “Lifnei Iver Lo Sitein Michshol.” [This prohibition applies even if the parent plans to forgive his child if they retaliate back. This prohibition applies even if one assesses that his child will not physically retaliate against him, but will speak against him and transgress the obligation to fear one’s parent. This prohibition applies even if one’s intent in hitting the child is for educational purposes to discipline the child make him into a good person. However, some Poskim permit hitting an adult child who is in the midst of performing a transgression in order to stop him from doing it.]
Until what age may one hit a child: A child is considered an adult in this regard from age 24 years old. The main time of educating a child is from age 16-24. Prior to age 16 the child does not have enough maturity to fully receive reproof from his parent, and one is thus not to chastise him and give him too heavy of a punishment. After 24 years old however there is worry that perhaps the child will rebel and fight back. [If however the child is already married, then he may no longer be hit by his father even if he is below the above age. Likewise, if the child is already looked upon as an adult by society, he may no longer be hit, irrelevant of age. Likewise, if the child is of age and/or of temperament that he would retaliate for being hit, such as by hitting his parent back or cursing him, then he is considered an adult in this matter and is forbidden to be hit even if he is under Bar or Bas Mitzvah. Likewise, if the child is of an age that he may go off the Derech as a result of being hit by his father, then it may be forbidden to hit the child.]
Sparks of Chassidus
A Chassid does not hit a child:
The Rebbe Rayatz once related: A father who hits his child may be a Tzadik, compassionate and righteous, although a Chassid he is not, as a Chasid does not hit.
Hitting one’s child should bring him pain:
Even when one is forced into reprimanding his child through physically hitting him, this should cause him much pain to the point he feels like crying. A story is told of Rav Yitzchak Shaul, a dear colleague of Reb Baruch, the father of the Alter Rebbe, that his father wept bitterly after smiting his child for cruel behavior.
Coming up in part 2:
- For what reasons may a child be hit?
- How hard may one hit?
- May one hit out of anger?
 Admur Hilchos Nizkei Guf Vanefesh 4; Michaber Y.D. 240:20; Rama Y.D. 233:1 regarding a child who makes vows; Kitzur Shulchan Aruch 143:18; 165:1; 184:2; Pesakim Uteshuvos 240:53
 Admur Hilchos Nizkei Guf Vanefesh 4 in parentheses; Admur 156:9; Kitzur Shulchan Aruch 184:2
 Iyun yaakov Moed Katan 17; Yifei Laleiv 3:35
 Michaber Y.D. 240:20; Admur ibid “small children”; Moed Katan 17a
 Michaber ibid; Rambam Mamrim 6:9; Moed Katan ibid; Kitzur Shulchan Aruch 143:18
 Birkeiy Yosef 240:14
 Aguda Kiddushin 1:26; Sdei Chemed Mareches Vav Kelal 24:14
Other opinions: Some Poskim rule it is permitted to hit an adult child for educational purposes such as for him to learn Torah or a profession. [Sdei Chemed ibid in name of Ritva Kiddushin 32a]
 Seder Halacha Hilchos Deios 6; Gevuros Yitzchak Inyan Gittin 58
 Admur Hilchos Talmud Torah 1:6; Second opinion in Rama 240:20 as explained in Shach 240:21; Opinion in Beis Yosef 334
Other opinions: Some Poskim rule it is forbidden to hit a child from age 22. [Rama 240:20 says “22 or 24” and Shach 240:21 explains that this is a dispute in Poskim, some say 22 and some say 24; Rashal Yam Shel Shlomo Kiddushin 68, brought in Pischeiy Teshuvah 240:17; Opinion in Kiddushin 30a and so rules Rashi ibid] Some Poskim rule the prohibition applies at age 22 although excommunication is only given from age 24. [Rashal ibid, brought in Pischeiy Teshuvah 240:17]
 Admur ibid based on merge of the two opinions in Kiddushin ibid; See Igros Kodesh 2:168
 Admur Hilchos Talmud Torah 1:6; Rashi Kiddushin ibid; Birkeiy Yosef 240:15
 Rashal Kiddushin 68, brought in Pischeiy Teshuvah 240:17
 See Rashal ibid
 Ritva Moed Katan 17a, brought in Birkeiy Yosef 240:15; Chayeh Adam 67:21; Kitzur Shulchan Aruch 143:18; Pela Yoeitz Erech Hakaha; Hagahos Imrei Baruch 240; Aruch Hashulchan 240:42; Beis Efraim Y.D. 76; Rav Akiva Eiger in name of Piskeiy Tosafus Moed Katan 3:76; This does not contradict the Rama/Admur ibid as they mentioned the average age regarding this matter, although in truth the determining factor is whether the child will become obedient or retaliate back. [Ritva ibid]
 See Beir Moshe 5:10-4 based on dispute between Shach and Taz 334:1
 Sefer Hasichos 5704 p. 15
 Memoirs Vol. 1 p. 334 [English edition]