Shaykh al-Haytham ibn Jamil {May Allah have Mercy upon them} said:
الإمام مالك أنه سئل عن ثماني وأربعين مسألة فقال في اثنين وثلاثين منها: لا أدري
“I heard Imam Malik {May Allah have Mercy upon him} being asked about 48 questions and he replied to 32 of them by saying, ‘I don’t know.’”
[al-Jami’ al-Bayan il-’Ilm wa-Fadlihi, Volume 2 pg. 25]