In the above exerpt from Mishnah Berurah, the author cites as a halachic source the book Tanya, written by the famed Chasidic master Rabbi Shneur Zalman of Liadi, also known as the first Lubavitcher Rebbe. He goes on to say that the view of the Tanya is opposed by the book Dagul meRevavah, written by Rabbi Yechezkel Landau (aka the Noda bYhudah, after the name of his great work of responsa), but rules in favor of the Tanya’s opinion. The irony here is that Rabbi Landau was among the most vehement opponents (“misnagdim”) of Chasidism in his time, even though Rabbi Landau’s own cousin was the wife of none other than the Baal Shem Tov (Rabbi Israel Baal Shem), the founder of the Chasidic movement. The further irony is that Rabbi Israel Meir Kagan, author of Mishnah Berurah, while certainly in his time took no part in the feud between the Chasidim and Misnagdim (the feud had mostly died away by his time), could squarely be identified as a leader of the non-Chasidic segment of Eastern European Jewry. Nevertheless, clearly, with no pro-Chasidic bias on his side, armed with purely legal tools of judgment, rules in favor of the view of Tanya against that of Dagul meRevavah. Fascinating.