What is the evidence that Joseph, peace be upon him, saw, which is mentioned in the Almighty's saying: "had he not seen the evidence of his Lord"?

Scholars have differed concerning the specific proof that Yusuf (peace be upon him) saw. Some said that he was called to desist, others that he saw the image of his father, and yet others that he saw the woman covering her idol, so he felt ashamed before God, while some said he saw Quranic verses written. The correct view is that the proof was one of God's signs that Yusuf (peace be upon him) saw, which strengthened his faith and caused him to abstain from sin. No specific determination of this proof has been mentioned in the Book or the Sunnah, so we must stop at that.