I asked Abu ‘Abdillah (a.s.) about the words of Allah, the Most Majestic, the Most Holy, ‘Exercise patience as the messengers who possessed determination had exercised patience. . . . ’(46:35) The Imam said, ‘They were Noah, Abraham, Moses, Jesus and Muhammad (a.s.).’ I then asked, ‘How did they become messengers who possessed great determination?’ The Imam replied, ‘It was because Noah had received a book from Allah and a system of laws and those who came after Noah, they followed his book and his system of laws until Abraham came with books and firm determination. He left the book of Noah aside but not out of rejection. Thereafter every prophet followed the system of laws of Abraham and his books (al-Suhuf) until Moses came with the Torah, his system of laws and with firm determination. He left the books (al-Suhuf) aside. Every prophet thereafter followed the Torah and the system of laws of Moses until Jesus came with the Gospel and firm determination. He left aside the system of laws of Moses. Every prophet thereafter followed the system of laws of Jesus until Prophet Muhammad (a.s.) came. He brought the Holy Quran and his system of laws (the Shari’a). All that is lawful in his system of laws will remain lawful until the Day of Judgment and all that is unlawful in his system of laws will remain unlawful until the Day of Judgment. This is how the messengers who possessed firm determination have been.’”