What is the ruling of Islamic law regarding an imam who says that our master Abraham, the Beloved of God, committed a sin when he told Pharaoh that Sarah was his sister?

It is not permissible to describe prophets as erring, and if it is intended as a disparagement, it is an act that expels one from the fold of Islam. What was narrated from the Imam concerning the errors of Ibrahim (peace be upon him) might be a misexpression, and perhaps he meant what is stated in the authentic Hadith (definition) from the Prophet (peace and blessings be upon him) that Ibrahim only uttered three "falsehoods": two for the sake of Allah and one concerning Sarah. Scholars have clarified that the use of the word "falsehood" (كذب) here is not to be taken literally, as reason dictates that prophets are trustworthy. Rather, these statements appeared as falsehoods to the listener, or were uttered in a state of extreme fear. Lying in such situations might be considered good to bear the lesser of two harms. The tyrant who took Sarah was not Pharaoh, but another person whose name scholars have differed upon.