who has saved us and called us to a life of consecration — not for anything we have done but because he chose to do it himself, by the grace which he gave us ages ago in Christ Jesus
that is, if you adhere to the foundations and stability of the faith, instead of moving away from the hope you have learned in the gospel, that gospel which has been preached to every creature under heaven, and of which I Paul was made a minister.
Those 'on the rock' are people who on hearing the word welcome it with enthusiasm, but they have no root; they believe for a while and fall away in the hour of trial.
Consider both the kindness and the severity of God; those who fall come under his severity, but you come under the divine kindness, provided you adhere to that kindness. Otherwise, you will be cut away too.
indeed Simon himself believed, and after his baptism kept close to Philip, utterly astonished to see the signs and striking miracles which were taking place.