Al-Adab Al-Mufrad, Hadith 880 ⓘ
Nafi' said, "Ibn 'Umar used to strike his son for making grammatical mistakes."
حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ: حَدَّثَنَا سُفْيَانُ، عَنْ عُبَيْدِ اللهِ، عَنْ نَافِعٍ قَالَ: كَانَ ابْنُ عُمَرَ يَضْرِبُ وَلَدَهُ عَلَى اللَّحْنِ.
also referenced under: Book 37, Hadith 6 (In-Book) & Book 37, Hadith 880 (English)