When he is about to sound (otan mellh salpizein). Indefinite temporal clause with otan and the present active subjunctive of mellw and the present (inchoative) active infinitive of salpizw, "whenever he is about to begin to sound" (in contrast to the aorist in Psalms 11:15 ). Then (kai). So in apodosis often ( Psalms 14:10 ). Is finished (etelesqh). First aorist passive indicative of telew, proleptic or futuristic use of the aorist as in 1 Corinthians 7:28 . So also Revelation 15:1 . The mystery of God (to musthrion tou qeou). This same phrase by Paul in 1 Corinthians 2:1 ; Colossians 2:2 . Here apparently the whole purpose of God in human history is meant. According to the good tidings which he declared (w euhggelisen). "As he gospelized to," first aorist active indicative of euaggelizw, a rare use of the active as in Colossians 14:6 with the accusative. See the middle so used in Galatians 1:9 ; 1 Peter 1:12 . See Amos 3:7 ; Jeremiah 7:25 ; Jeremiah 25:4 for this idea in the O.T. prophets who hoped for a cleaning up of all mysteries in the last days.