And another apostle - our apostle - said the believer is dead to the Law.
Is it possible that either John's use of "commandments" means something other than the Law . . . or . . . it does mean the Law but he was speaking to an audience that would be specially enabled to abide in the Law, while Paul was talking to another group that was dead to it?
The requirements of God concerning man since the time of Adam are ever the same, namely He requires perfect obedience. The grace of God has not been given to one portion of mankind to the exclusion of the rest. Paul says, "... the grace of God that bringeth salvation hath appeared to all men," Titus 2:11. The same grace that enabled Christ to render perfect service is available to us.
All the apostles are ours. Paul says, "For all things are yours; Whether Paul, or Apollos, or Cephas..." 1Corinthians 3:21,22. The inspired writers all have a message to us from God.
We dare not pick a part of the Bible as essential and ignore another as nonessential. The inspired Paul says, "All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of God may be perfect, throughly furnished unto all good works," 2Tim 3:16,17