The goal of this command is love, which comes from a pure heart and a good conscience and a sincere faith. Some have wandered away from these and turned to meaningless talk. The man who wants to be a teacher and straighten out others but wanders away from a pure heart, a good conscience and a sincere faith will make a lot of meaningless noise. As Paul demanded that correct doctrine be used, he sometimes referred to it as sound doctrine. Thus, Paul is saying that correct doctrine is necessary in order to be spiritually healthy.
Sound doctrine promotes good spiritual health but there is a danger.
An overemphasis on doctrinal issues will absolutely choke out our spirituality. We will turn into legalists unless we find the right balance. But in your hearts set apart Christ as Lord. Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience, so that those who speak maliciously against your good behavior in Christ may be ashamed of their slander.