Be strengthened (endunamou). Present passive imperative of endunamow. See already 1 Timothy 1:12 ; Romans 4:20 ; Philippians 4:13 ; Ephesians 6:10 . "Keep on being empowered," "keep in touch with the power." In the grace that is in Christ Jesus (en th cariti th en Cristwi Ihsou). Where the power is located. Christ is the dynamo for power only when and while we keep in touch with him.