There's an old saying often attributed to John Wesley (bonus points if anyone can find the actual quote):
"And even if they come to you with sound teaching and persuasive words, and have not love, do not listen, do not listen, do not listen!"
In other words, if even the best preacher, teacher, or evangelist makes his case persuasively and consistently, and provides chapter and verse for all his claims, yet fails to exhibit any care for those around him (discounting any personality quirks, genuine shyness, rushed schedules, etc.) then it's best to take what they have to say with a grain of salt (I John 2:15). If you don't understand what it means to love, then "the greatest of these" (I Cor. 13:13) is missing from even the most convincing message of faith and hope.
As part of our recent teaching theme on false prophets, Romans 16 came to mind -- particularly vv. 16 and 17, which gives a short outline of the motivations of errant teachers. But the real lesson surrounds those two verses. Basically, it's love.
Notice that Paul didn't take time to greet everyone he could think of as part of a postscript, addendum, or some afterthought, but as an integral part of his teaching in chapter 16. Yes, I understand this may have been stream-of-consciousness writing and poor Tertius (v. 22) was doing what he could to keep up with Paul's dictation. However, it still says plenty that the Apostle himself took the time to greet the church at Rome person by person by person. And then he caps it off with a doxology.
Romans 16 is cited below, minus the verse numbers. The greetings are highlighted in blue, and teachings are in yellow. Take a moment and read over each Roman name (some of which are awesome and Gladiator-esque!) among the 28 person-specific greetings. And notice a reference to a house church!
Yes, it's a lot to read, but that's the point ... and settle for nothing less in your teachers.
I commend to you our sister Phoebe, a deacon of the church at Cenchreae, so that you may welcome her in the Lord as is fitting for the saints, and help her in whatever she may require from you, for she has been a benefactor of many and of myself as well. Greet Prisca and Aquila, who work with me in Christ Jesus, and who risked their necks for my life, to whom not only I give thanks, but also all the churches of the Gentiles. Greet also the church in their house. Greet my beloved Epaenetus, who was the first convert in Asia for Christ. Greet Mary, who has worked very hard among you. Greet Andronicus and Junia, my relatives who were in prison with me; they are prominent among the apostles, and they were in Christ before I was. Greet Ampliatus, my beloved in the Lord. Greet Urbanus, our co-worker in Christ, and my beloved Stachys. Greet Apelles, who is approved in Christ. Greet those who belong to the family of Aristobulus. Greet my relative Herodion. Greet those in the Lord who belong to the family of Narcissus. Greet those workers in the Lord, Tryphaena and Tryphosa. Greet the beloved Persis, who has worked hard in the Lord. Greet Rufus, chosen in the Lord; and greet his mother — a mother to me also. Greet Asyncritus, Phlegon, Hermes, Patrobas, Hermas, and the brothers and sisters who are with them. Greet Philologus, Julia, Nereus and his sister, and Olympas, and all the saints who are with them. Greet one another with a holy kiss. All the churches of Christ greet you.I urge you, brothers and sisters, to keep an eye on those who cause dissensions and offenses, in opposition to the teaching that you have learned; avoid them. For such people do not serve our Lord Christ, but their own appetites, and by smooth talk and flattery they deceive the hearts of the simple-minded. For while your obedience is known to all, so that I rejoice over you, I want you to be wise in what is good and guileless in what is evil. The God of peace will shortly crush Satan under your feet. The grace of our Lord Jesus Christ be with you.Timothy, my co-worker, greets you; so do Lucius and Jason and Sosipater, my relatives. I Tertius, the writer of this letter, greet you in the Lord. Gaius, who is host to me and to the whole church, greets you. Erastus, the city treasurer, and our brother Quartus, greet you.Now to God who is able to strengthen you according to my gospel and the proclamation of Jesus Christ, according to the revelation of the mystery that was kept secret for long ages but is now disclosed, and through the prophetic writings is made known to all the Gentiles, according to the command of the eternal God, to bring about the obedience of faith— to the only wise God, through Jesus Christ, to whom be the glory forever! Amen. (NRSV)