He promised afore (proepēggeilato). First aorist middle of proepaggellō for which verb see note on 2Co 9:5.
By (dia). Through, by means of, intermediate agency like Mat 1:22 which see.
In the holy scriptures (en graphais hagiais). No article, yet definite. Perhaps the earliest use of the phrase (Sanday and Headlam). Paul definitely finds God’s gospel in the Holy Scriptures.