الكافي 2/1/36/7

7. A number of our people have narrated from Ahmad ibn Muhammad ibn Khalid from ‘Uthman ibn ‘Isa from Mufaddal ibn ‘Umar who has said the following: “Once I was in the presence of abu ‘Abd Allah عليه السلام . We spoke about deeds and I said, ‘My deeds are the weakest.’ The Imam said, ‘Calm down. Ask forgiveness from Allah.’ Then the Imam said to me, ‘A little deed with piety is better than a great deal of deeds without piety.’ I then asked, ‘Can there be a great deal of deeds without piety?’ The Imam said, ‘Yes, it is true. It is like a man who feeds people, who is kind to his neighbors and entertains people at his home, but when a door to unlawful matters opens he enters such a door. Such are deeds without piety. There can be another person who does not have such deeds but when a door to unlawful matters opens he does not enter into such doors.’”