For yourselves know (autoi gar oidate). This explanatory gar takes up in 1Th 2:1-12 the allusion in 1Th 1:9 about the “report” concerning the entrance (eisodon, way in, eis, hodon), unto you (tēn pros humās). Note repeated article to sharpen the point. This proleptic accusative is common enough. It is expanded by the epexegetic use of the hoti clause that it hath not been found vain (hoti ou kenē gegonen). Literally, that it has not become empty. Second perfect active (completed state) of ginomai. Every pastor watches wistfully to see what will be the outcome of his work. Bengel says: Non inanis, sed plena virtutis. Cf. 1Th 1:5. Kenos is hollow, empty, while mataios is fruitless, ineffective. In 1Co 15:14, 1Co 15:17 Paul speaks of kenon to kērugma (empty the preaching) and mataia hē pistis (vain the faith). One easily leads to the other.