Hilchos Shabbos siman shin pei zayin seif aleph 10 minutes exploring the path Chovas Halevavos Shaar Yichud Hamaaseh perek hei part 39, Sefer Mishna Brura, Chapter 5, Siman 387, Seif 1, Shulchan Aruch Orach Chaim

Rabbi Gabi Fried