ISB ~ 2 Timothy 3 v15

the Sacred Writings:i.e., the writings of the OT. The NT had not yet been written when Timothy was a young boy. Jewish children often began instruction in the Torah at age five (Mishnah, Aboth 5, 21).

for salvation:The books of the OT point the way to Christ (Rom 1:2-3) and continue to instruct his disciples for life in the New Covenant (Rom 15:4) (CCC 121-23, 128-30).