An emphatic expression calling special attention to what follows. Compare 1Co 10:1; 1Th 4:13.
Have some fruit (τινὰ καρπὸν σχῶ)
For the phrase, compare Rom 6:22. A metaphorical statement of what is stated literally in Rom 1:11. Not equivalent to bear fruit, but to gather as a harvest. Compare Joh 4:36; Phi 1:22; Col 1:6. Fruit is a favorite metaphor with Paul. He uses it in both a good and a bad sense. See Rom 7:4, Rom 7:5; Rom 6:22; Gal 5:22.