A.T. Robertson Commentary Luke 13:4

"Or those eighteen, upon whom the tower in Siloam fell, and killed them, think ye that they were offenders above all the men that dwell in Jerusalem?" — Luke 13:4 (ASV)

The tower in Siloam (ο πυργος εν Σιλωαμ). Few sites have been more clearly located than this. Jesus mentions this accident (only in Luke) of his own accord to illustrate still further the responsibility of his hearers. Jesus makes use of public events in both these incidents to teach spiritual lessons. He gives the "moral" to the massacre of the Galilean pilgrims and the "moral" of the catastrophe at Siloam.

Offenders (οφειλετα). Literally,

debtors , not sinners as in verse 2 and as the Authorized Version renders here. See 7:41; 11:4; Matthew 6:12; 18:24-34.