Albert Barnes on Matthew 9:9

Sitting at the receipt of custom. That is, at the place where custom, or tribute, was received; or, in other words, he was a publican, or tax-gatherer. Mt 5:47. This man was Matthew, the writer of this gospel. The same account is found in Mk 2:14, Lk 5:27,28. Both those evangelists call him Levi. That it was the same man is known by the circumstances in which he was called being the same in all the evangelists, and by all concurring in the statement that our Saviour was present at a feast soon after he called him, and by the fact that Levi is not mentioned in the catalogue of the apostles. The Jews were in the habit of giving several names to the same person. Thus Peter was also called Simon and Cephas. It is worthy of remark, that Luke has mentioned a circumstance favourable to Matthew, which Matthew himself has omitted. Luke says, "he left all." Had Matthew said this, it would have been a commendation of himself, utterly unlike the evangelists. No men were ever farther from praising themselves than they were.

(s) "And as Jesus passed" Mk 2:14, Lk 5:27