Samaritans worshiped on Mount Gerizim, as Moses commanded (Deut. 11-12) and where had had altars built. Jews knew that God had later commanded worship in Jerusalem, where he had Solomon build the Temple. This was the true place of worship. In a sense, the two temples themselves became idols for them. Both believed that the Messiah would come and justify their position. Into this argument walks Jesus; what will Messiah say? 
Scripture: Exodus 20:4-6; John 4:1-26