A.T. Robertson Commentary Luke 8:39

"Return to thy house, and declare how great things God hath done for thee. And he went his way, publishing throughout the whole city how great things Jesus had done for him." — Luke 8:39 (ASV)

Throughout the whole city (καθ' ολην την πολιν). Mr 5:20 has it "in Decapolis." He had a great story to tell and he told it with power. The rescue missions in our cities can match this incident with cases of great sinners who have made witnesses for Christ.