Philippians 4:8-9; NKJV
8 Finally, brethren, whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy — meditate on these things.
9 The things which you learned and received and heard and saw in me, these do, and the God of peace will be with you.
If we mediate on these things and learn and receive the Apostolic doctrine and do them, the God of peace will be with us.
If we think on other things and we don't learn and receive the Apostolic doctrine and do them, the God of peace will not be with us.
Mediate on these things...
