{When he shall come} (hotan elth(8869)). Second aorist active
subjunctive with hotan, future and indefinite temporal clause
(Robertson, _Grammar_, pp. 971ff.) coincident with en t(8869)
apokalupsei in verse  7 . {To be glorified} (endoxasth(886e)ai).
First aorist passive infinitive (purpose) of endoxaz(935c), late
verb, in N.T. only here and verse  12 , in LXX and papyri. {In
his saints} (en tois hagiois autou). The sphere in which Christ
will find his glory at the Revelation. {And to be marvelled at}
(kai thaumasth(886e)ai). First aorist passive infinitive (purpose),
common verb 	haumaz(935c). {That believed} (	ois pisteusasin). Why
aorist active participle instead of present active pisteuousin
(that believe)? Frame thinks that Paul thus reassures those who
believed his message when there ( 1Th 1:6ff.  2:13f. ). The
parenthetical clause, though difficult, falls in with this idea:
{Because our testimony unto you was believed} (hoti episteuth(880a)to marturion h(886d)(936e) eph' humas). Moffatt calls it an anti-climax.
{On that day} (en t(8869) h(886d)er(8369) ekein(8869)). The day of Christ's
coming ( 2Ti 1:12,18  4:8 ).