Should one read the books of Al-Bayhaqi: "Shu'ab al-Iman" (Branches of Faith) and "Al-Sunan al-Kubra" (The Major Sunan) in their entirety, knowing that he was Ash'ari in creed, and are they in agreement with the creed of Ahl al-Sunnah wal-Jama'ah, or is it necessary to acquire knowledge from other books before them?

What the questioner mentioned, that Al-Bayhaqi was Ash'ari, is problematic only in books related to Names and Attributes and creed, such as the book "Al-Asma' wa al-Sifat" (The Names and Attributes) and "Al-I'tiqad" (The Creed). As for the book "Shu'ab al-Iman" (Branches of Faith), it is closer to books of spiritual edification, conduct, ethics, and the deeds of the hearts. And the book "Al-Sunan al-Kubra" (The Major Sunan) is about branches of jurisprudence. Therefore, these two books do not pose a problem when viewed on their own.