To what extent is the hadith true concerning the conversion to Islam of Umar ibn al-Khattab, which includes his hearing of Surat Taha from his sister and her husband, his performing of ghusl, and then his reading of the scripture that was with them?

The story mentioned was narrated by Al-Tabarani and others with different wordings, which indicates that it has an origin. However, its chain of transmission is not authenticated, as Al-Dhahabi stated that it is denounced (munkarah). The Salaf did not scrutinize historical accounts and biographies unless they pertained to creed or legal rulings, or contradicted the general principles of Islam. Therefore, some of them said: "Let the reader know that biographies (siyar) gather what is sound and what is denounced."