الكافي 1/4/82/5

5. Al-Husayn ibn mmd has narrated from Mu‘alla ibn Muhammad from al-Hassan ibn Ali al-Khazzaz from ‘Abd al-Karim ibn ‘Umar al-Khath‘ami from al-Fadl ibn Yasar who has said the following. “I asked abu Ja’far عليه السلام , ‘Is there a definite time for this matter (the rise of al-Mahdi with Divine Authority)?” He said, “Those who set a definite time have lied, those who set a definite time have lied, those who set a definite time have lied. When Musa (Moses) came out to delegate before his lord and gave the people a definite time for his return and Allah added an other ten days his people said, ‘He has broken his promise.’” They then did what they did. When we say a hadith (make a statement to you) and if our hadith comes true you should say, “Allah has spoken the truth.” If we say a hadith to you ( make a statement) and if doe not come true, you should say, “Allah has spoken the truth.” You will be rewarded twice.”