According to the opening paragraph,what keeps sinners from falling to hell?

Edwards' sermon seeks to impress upon the faithful the fact that God is, at no point,
"under any obligation to keep any natural man" out of hell, and that indeed the
natural state of all men is to be condemned to hell. This is, Edwards says, implied by the
suggestion that their feet are only waiting to "slip" into that pit: they stay out of
it only because "God's appointed time has not come," and are saved only "at the
mere pleasure" of God himself.

The opening paragraph makes a concise
case which Edwards then goes on to explain over the course of the sermon that follows. It
laments that the Israelites did not understand the words spoken to them, that they would fall
"in due time." Edwards then goes on to...