'Concerning' in the Bible

Concerning which salvation the prophets sought and searched diligently, who prophesied of the grace that'should come unto you:

but sanctify in your hearts Christ as Lord: being ready always to give answer to every man that asketh you a reason concerning the hope that is in you, yet with meekness and fear:

Beloved, think it not strange concerning the fiery trial among you, which cometh upon you to prove you, as though a strange thing happened unto you: