saw = viewed with attention. Greek. theaomai.App-133.
publican = toll-collector, or tax-gatherer. See on Luk_3:12.
Levi. There can be no doubt about Levi and Matthew being different names for the same person (Mat_9:9. Mar_2:14). For similar changes, at epochs in life, compare Simon and Peter, Saul and Paul. Matthew is an abbreviation of Mattathias = Gift of God, and he is so called after this. "Sitting "shows he was a custom-house officer.