He is to be respected for his work's sake and supported financially, if need be, because in verse 18 the apostle goes right on to define honour in that way. The elders and principally of course the preachers who are elders are watching out for the health of the church.
Elsewhere, in 1 Corinthians, the Apostle Paul says, do you think that that law was given for the benefit of the oxen? No, for our sakes, for the sake of preachers. In other words, in the ancient law, God teaches the people to treat their animals kindly and well because that is right, but also so that people will learn principles that, at their highest, are applied to the church. Obviously, if you must allow the oxen to eat while they are working, how much more must you allow those who feed the people of God spiritually to be supported and to live from their labours? We see how the ancient law works. The law seems at first sight to be just about oxen, but it's much more profound than that. It's teaching people principles which apply all the way up the scale to the servants of the Lord.
The teaching of this is that Christian workers are to be paid and supported. That is part of our calling. The Lord calls us together as a company of his people, and one of the purposes is that we shall support Christian workers so that the word of God will be proclaimed, the gospel will go out, God's standards in the church will be studied and declared to the people by preachers. We gather together and we steward our resources so that the word of God may go forth and have its maximum impact, and that is why the preachers must be supported.
The second part of this verse is very interesting. ‘The labourer is worthy of his reward.’ Was Luke's Gospel, contrary to what modern scholarship imagines, already written, so that here the Apostle Paul in 1 Timothy can quote from it? This is a quotation of the Lord Jesus as it appears in Luke's Gospel. Certainly, it is very possible that what the Lord said was well known and had been passed down already orally. But then Luke was a very good friend of Paul, as we know from the book of Acts, and travelled with him a great deal. Does it mean that as Luke was writing his Gospel, Paul was one of the people he would show it to, constantly and frequently?