'Well grounded' in the Bible

Now a certain Jew named Apollos, a native of Alexandria [Egypt] and an effective speaker, who was well-grounded in the [Old Testament] Scriptures, came to Ephesus.

[and He will do this] if you continue in the faith, well-grounded and steadfast, and not shifting away from the [confident] hope [that is a result] of the gospel that you have heard, which was proclaimed in all creation under heaven, and of which [gospel] I, Paul, was made a minister.

securing to themselves a well-grounded expectation of obtaining hereafter an immortal life.

Now faith is a well-grounded assurance of that for which we hope, and a conviction of the reality of things which we do not see.