Question: I’ve always waited three hours after eating meat before eating milky foods though was recently told that this custom has no basis and I must wait 6 hours. Do I need to change?
Answer: The Gemara (Chulin 105a) relates that Mar Ukva would wait between eating a meat meal and a milky one. The poskim debate how long the interval between meals is.
The Shulchan Aruch (YD 89:1) writes that this is six hours while Rambam (Maachalos Asuros 9:28) writes that this is about six hours. According to many poskim (Chochmas Adam 40:13, Pischei Teshuva 87:4, and Aruch Hashulchan 89:7) this means six complete hours, while others (Ohr Yitzchak YD 4) write that it means over five and a half hours.
Dutch Jews follow the Rema (YD 89:1) and wait just one hour or seventy two minutes (Kreisi Upleisi 89:3).
Many Jews, especially in the UK, follow the German custom of waiting three hours, though there is a debate as to the origin of this view.
Indeed, many of the German poskim themselves write that one should wait six hours (Horeb 453; Kreisi Upleisi 89:3).
Many quote Rabbeinu Yerucham (Kitzur Issur Veheter 39) who mentions waiting three hours, though R’ Asher Zvi Lunzer (Madanei Asher 41) claims that this is a misprint as in the unabridged sefer (Sefer Adam 15:28) he writes that one must wait at least six hours.
Shorshei Minhag Ashkenaz writes that there is no real source though postulates that the three hours came about by German Jews who originally kept one hour who later wanted to compromise with those waiting six hours.
The Darkei Teshuva (89:6) and Mizmor Ledovid (YD 89:6) explain that it is based on the short winter days when people would typically wait three hours between their meals or that it is based on the calculation of shaos zemanios (halachic hours that vary by season).Irrespective of the source, waiting three hours after meat has become a real minhag mentioned among the contemporary poskim (See Yabia Omer YD 1:4:12), and one who already waits three hours does not need to change one’s minhag to wait six hours (Madanei Asher).