Jamieson, Fausset and Brown on Isaiah 43:27

27. first father--collectively for "most ancient ancestors," as the parallelism ("teachers") proves [Maurer]. Or, thy chief religious ministers or priests [Gesenius]. Adam, the common father of all nations, can hardly be meant here, as it would have been irrelevant to mention his sin in an address to the Jews specially. Abraham is equally out of place here, as he is everywhere cited as an example of faithfulness, not of "sin." However, taking the passage in its ultimate application to the Church at large, Adam may be meant.

teachers--literally, "interpreters" between God and man, the priests (Job 33:23; Mal 2:7).