Whether Luke intends to distinguish between the Twelve as “apostles” and the others who regularly followed Him as “disciples” (see v. 1) is not clear. Verses 5, 6 are concerned with the power of faith.
Increase our faith.
See on Matt. 17:20. The context makes it probable that this request came at a time other than the occasion represented in Luke 17:1-4 (see on v. 1). It seems that the “apostles” felt they had a measure of faith, but realized that it was not adequate.