In Act 19:22, sent by Paul with Timothy to Macedonia from Ephesus. Rom 16:23, the city-treasurer who sends salutations. He cannot be certainly identified with the one mentioned here. The writer merely selects names of well-known companions of Paul.
See Act 22:4; Act 21:9.
By Paul mostly in a moral sense, as weak in the faith, Rom 4:19; the law was weak, Rom 8:3; the weak brother, 1Co 8:11. Of bodily sickness, Phi 2:26, Phi 2:27.