Adam Clarke on Acts 13:51

They shook off the dust of their feet against them - This was a very significant rite; by it, they in effect said: Ye are worse than the heathen: even your very land is accursed for your opposition to God, and we dare not permit even its dust to cleave to the soles of our feet; and we shake it off, in departing from your country, according to our Lord's command, (Mat 10:14), for a testimony against you, that we offered you salvation, but ye rejected it and persecuted us. The Jews, when travelling in heathen countries, took care, when they came to the borders of their own, to shake off the dust of their feet, lest any of the unhallowed ground should defile the sacred land of Israel.

Came unto Iconium - According to Strabo, Iconium was a small fortified town, the capital of Lycaonia, at present called Cogni. "Lycaonia was a province at the back of Pamphylia, higher up in Asia Minor, and to the northeast of Pamphylia." Pearce.