Paul wrote, under inspiration, at 2 Timothy 3:8 Now in the way that Jan?nes and Jam?bres resisted Moses, so these also go on resisting the truth, men completely corrupted in mind, disapproved as regards the faith. 9 Nevertheless, they will make no further progress, for their madness will be very plain to all, even as the [madness] of those [two men] became. 10 But you have closely followed my teaching, my course of life, my purpose, my faith, my long-suffering, my love, my endurance, 11 my persecutions, my sufferings, the sort of things that happened to me in Antioch, in I?co?ni?um, in Lys?tra, the sort of persecutions I have borne; and yet out of them all the Lord delivered me. 12 In fact, all those desiring to live with godly devotion in association with Christ Jesus will also be persecuted. 13 But wicked men and impostors will advance from bad to worse, misleading and being misled.
14 You, however, continue in the things that you learned and were persuaded to believe, knowing from what persons you learned them 15 and that from infancy you have known the holy writings, which are able to make you wise for salvation through the faith in connection with Christ Jesus. 16 All Scripture is inspired of God and beneficial for teaching, for reproving, for setting things straight, for disciplining in righteousness, 17 that the man of God may be fully competent, completely equipped for every good work.
An alternative, but agreeable rendition of those verses is found in the NKJV.
2 Timothy 3:8 And even as Jannes and Jambres withstood Moses, so do these also withstand the
truth. Men corrupted in mind, reprobate concerning the faith.
2 Timothy 3:9 But they shall proceed no further. For their folly shall be evident unto all men, as
theirs also came to be.
2 Timothy 3:10 But thou didst follow my teaching, conduct, purpose, faith, longsuffering, love,
patience,
2 Timothy 3:11 persecutions, sufferings. What things befell me at Antioch, at Iconium, at Lystra;
what persecutions I endured. And out of them all the Lord delivered me.
2 Timothy 3:12 Yea, and all that would live godly in Christ Jesus shall suffer persecution.
2 Timothy 3:13 But evil men and impostors shall wax worse and worse, deceiving and being deceived.
2 Timothy 3:14 But abide thou in the things which thou hast learned and hast been assured of, knowing of whom thou hast learned them.
2 Timothy 3:15 And that from a babe thou hast known the sacred writings which are able to make thee wise unto salvation through faith which is in Christ Jesus.
2 Timothy 3:16 Every scripture inspired of God [is] also profitable for teaching, for reproof, for correction, for instruction which is in righteousness.
2 Timothy 3:17 That the man of God may be complete, furnished completely unto every good work.
Paul here refers to scripture in two sense. First as the tool needed for Godly purposes, and secondly as the foundation on which Timothy had built his knowledge of God and His purposes
According to that, all the "man of God" needs to be "fully equipped" is scripture, and obviously an understanding of that. Not the word of man, unless it can demonstrate full agreement with scripture.
That is why I rely purely on God's word, the bible, as the final arbiter of all things.