Adam Clarke on John 4:26

Jesus saith unto her, I - am he - Our Lord never spoke in such direct terms concerning himself to his own countrymen; nor even to his own disciples, till a little before his death. The reason given by Bishop Pearce is the following: The woman being alone when Jesus said it, and being a Samaritan, he had no reason to apprehend that the Samaritans, if they knew his claim, would disturb his ministry before the time of his suffering came; which seems to have been the reason why he concealed it so long from his own countrymen.