John Gill Commentary Philippians 3:16

"only, whereunto we have attained, by that same [rule] let us walk." — Philippians 3:16 (ASV)

Nevertheless, whereto we have already attained
Whatever degree of knowledge of Christ, and the truths of his Gospel, is attained to, let it be retained, and not departed from:

let us walk by the same rule ;
either the doctrine of justification by Christ's righteousness in particular, which is a rule of judgment concerning other things; for so far as they agree or disagree with this, they are to be received or rejected; or the Scriptures of truth, which are the rule of faith and practice, and the standard and test, to which all are to be brought and tried:

let us mind the same thing ;
be of one heart and affection to each other, (Romans 12:10) , and of the same judgment in the doctrines of the Gospel, (1 Corinthians 1:10) , and pursue the same measures; particularly press towards the same mark, and for the same prize the apostle did, (Philippians 3:14) , and be followers of him, as is exhorted to in (Philippians 3:17) .