Quartus [Quär'tus]—the fourth.
This name is associated with a quarternion of soldiers, that is, a file of four, the usual number for a night watch. Peter was placed under the guard of four quarternions of soldiers, or sixteen soldiers, in order that each might guard him three hours at a time (Acts 12:4).
It may be fitting at this point to discover the significance of the many friends Paul speaks of. Romans and Colossians are unique for their number of personal salutations. Paul himself was such a friendly person that friends gathered around him as moths do around a lighted lamp. In the majority of cases all we have is the mention of a name. Now and again Paul adds a brief, endearing term. But the fact that he mentions many by name, as in the case of Quartus, proves that he must have had some contact with them. Either he had met them on his journeys and they were blessed by his ministry, or they had ministered unto the apostle of their substance. By including their names in his letters, he gave them an imperishable memory.
There were multitudes of others who had labored with Paul in the Gospel, too numerous perhaps to be called by name. The apostle rejoiced, however, that their names, although not mentioned in his lists, were written in the Book of Life, and fully known of the Lord (Phil. 4:3). John also besought Demetrius to greet all his friends by name (3 John 14).