Based on many inquiries about a Halacha we posted a few day ago, it is worthwhile to review and clarify the position of the Poskim regarding the use of hard bar soap on Shabbat. Many Acharonim (later authorities) are machmir (stringent) and prohibit the use of hard soap. This is the ruling of Hacham Ben Sion, the Mishna Berura (siman 326) and the Ma'aseh Rokeach.
Moreover, the great Rabbi Shalom Laniado, Av Beit Din in Halab, clearly writes in a teshuva (responsa) cited in Shut Ma'aseh Ish that although some people were using hard soap on Shabbat, relying on the minority opinion of the Ginat Veradim, nonetheless, we do not follow this Rabbi, since many authorities disagree with him.
Hacham Ovadia, in Yabia Omer and other works found leniencies based on the Pachad Yitzhak and others that don't follow the Mishna Berura on this issue. He, therefore, wrote that in principle, there is room to be lenient. However, when it came to Halacha L’Maaseh (practical application of the Halacha) even Hacham Ovadia ruled, in one of his later works, Halichot Olam, "It is good to adopt the position of the Acharonim who are strict in this matter, and this is the accepted custom."
Some were under the mistaken impression that Hacham Ovadia permitted the use of hard soap, Lechathila. This is not true. Only under extenuating circumstances would Hacham Ovadia rule to rely on the "letter of the law" leniency. However, under ordinary circumstances, especially today that liquid soap is common, and it is easy to avoid these problems, one should not use hard soaps on Shabbat.
SUMMARY
Lechathila, one should not use hard bar soap on Shabbat, even according to Hacham Ovadia.
