14 But you must continue in the things which you have learned and been assured of, knowing from whom you have learned them,
15 and that from childhood you have known the Holy Scriptures, which are able to make you wise for salvation through faith which is in Christ Jesus.
16 All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness,
17 that the man of God may be complete, thoroughly equipped for every good work.
from whom (v.14) = lit. “of what persons (plural)” — Timothy was to remember who had taught him the Scriptures — especially Paul, but also his grandmother and mother (2 Timothy 1:5)
childhood (v.15) = infant — Timothy’s training, and that of every Jewish child, in the Old Testament, began when he was very young.
Christ Jesus (v.15) — the order of the names emphasizes His exaltation after His resurrection
all (v.16) = every — so, not referring to Scripture as a whole, but of each separate passage considered as a unit
Some commentaries make a case that Paul was only referring to the Old Testament here because that’s what Timothy would have been taught as a boy. It is true that the Old Testament was the only part of Scripture in existence when Timothy was a boy. But since 2 Timothy was the last of Paul’s letters and all the earlier ones would certainly have been known and read by Timothy by this time, and since Paul reminds Timothy to remember who — Paul — he heard the Scriptures from, there can be no doubt that Paul is referring also to his own writings and other New Testament writings. Especially since the entire book is encouraging Timothy to hold fast to the doctrine taught him by Paul — 2 Timothy 1:13; 2 Timothy 2:2. The idea that Paul backs off here and only tells Timothy that the Old Testament is inspired is ridiculous.
by inspiration of God (v.16) = lit. “God-breathed)
doctrine (v.16) = teaching
reproof (v.16) = conviction
correction (v.16) = restoration to an upright or right state
instruction (v.16) = training by instruction — everything that is included in the education of a child
thoroughly equipped (v.17) — a maritime term used for the fitting out of a ship for a long voyage so that all the needed supplies are included. The word translated “thoroughly equipped” shares a root with the word “complete” used earlier in the verse.