{For yourselves know} (autoi gar oidate). This explanatory
gar takes up in verses  1-12  the allusion in  1:9  about the
"report" concerning the entrance (eisodon, way in, eis,
hodon), {unto you} (	(886e) pros hum(8373)). 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 ken(8820)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.  1:5 . Kenos is hollow, empty, while
mataios is fruitless, ineffective. In  1Co 15:14,17  Paul
speaks of kenon to k(8872)ugma ({empty the preaching}) and mataia
h(8820)pistis ({vain the faith}). One easily leads to the other.