Is it valid to act upon ahad (single-narrator) hadith in matters of creed?

Question:
Is it permissible to act upon ahad (single-narrator) hadith in matters of creed?

Answer:
If a hadith is authentic from the Messenger of Allah (peace and blessings be upon him), it is obligatory to act upon it in matters of creed and other matters, because it is a hadith established from the Messenger (peace and blessings be upon him). There is no difference between it and mutawatir (mass-transmitted) hadith, because it is an authentic hadith; the criterion is authenticity. As long as it is authentic, it is the truth, and it is obligatory to act upon it in matters of creed and other matters. Yes.