A.T. Robertson Commentary Philippians 4:13

"I can do all things in him that strengtheneth me." — Philippians 4:13 (ASV)

I can do all things (παντα ισχυω). Old verb to have strength (ισχυς).

In him that strengtheneth me (εν τω ενδυναμουντ με). Late and rare verb (in LXX) from adjective ενδυναμος (εν, δυναμις). Causative verb to empower, to pour power into one. See same phrase in 1 Timothy 1:12 τω ενδυναμωσαντ με (aorist tense here). Paul has such strength so long as Jesus keeps on putting power (δυναμις) into him.