Sahih Bukhari, Chapter: Witnesses

A Jew from Hira asked me which one of the two periods Musa (i.e. Prophet Moses) completed. I said, "I don't know, (but wait) till I see the most learned Arab and enquire him about it." So, I went to Ibn Abbas and asked him. He replied, "Musa (Moses) completed the longer and better period." Ibn Abbas added, "No doubt, an apostle of Allah always does what he says."