We find in 1 Corinthians 16 four channels, so to speak, of ministry. First, the Apostle, sent direct from the Lord and by the Holy Spirit. Second, persons associated with the Apostle in his work, acting at his desire, and (in the case of Timothy) pointed out by prophecy. Third, an entirely independent laborer, partly instructed by others (see Acts 18:2626And he began to speak boldly in the synagogue: whom when Aquila and Priscilla had heard, they took him unto them, and expounded unto him the way of God more perfectly. (Acts 18:26)), but acting where he saw fit, according to the Lord and to the gift he had received. Fourth, one who gives himself to the service of the saints, as well as others who helped the Apostle and labored. Paul exhorts the faithful to submit themselves to such and to all those who helped in the work and labored.
He would also have them acknowledge those who refreshed his heart by their service of devotedness. Thus we find the simple and important principle according to which all the best affections of the heart are developed, namely, the acknowledgment of every one according to the manifestation of grace and of the power of the Holy Spirit in him.
The Christian submits to those who addict themselves to the service of the saints; he acknowledges those who manifest grace in a special way. They are not persons officially nominated and consecrated who are spoken of here. It is the conscience and the spiritual affection of Christians which acknowledges them according to their work—a principle valid at all times, which does not permit this respect to be demanded, but which requires it to be paid.
J. N. Darby (Synopsis on 1 Corinthians 16)