ما الفرق بين صيغتي "حدثنا فلان" و"عن فلان" في رواية الحديث؟

The phrases "حدثنا" (narrated to us) and "عن" (on the authority of) indicate the continuity of the chain of narration unless the narrator using "عن" is a mudallis (one who practices tadlis, i.e., conceals defects in the chain). "حدثنا" is stronger and clearer in indicating the continuity of the chain than "عن," because "عن" might be used in cases of both continuity and discontinuity.

If the narrator using "عن" is a mudallis, then the hadith is not established until it is confirmed that the narrator heard it directly from his sheikh. The majority view is that a hadith narrated with "عن" is considered continuous if it was possible for the narrators involved to have met each other, and provided that the narrator using "عن" is free from tadlis. The statement of a Muhaddith "حدثنا فلان قال حدثنا فلان" (So-and-so narrated to us, saying So-and-so narrated to us) is of a higher standing than his statement "حدثنا فلان عن فلان" (So-and-so narrated to us on the authority of So-and-so); since "عن" is used in concealing what was not heard directly.