A.T. Robertson Commentary 3 John 1:5

"Beloved, thou doest a faithful work in whatsoever thou doest toward them that are brethren and strangers withal;" — 3 John 1:5 (ASV)

A faithful work (πιστον). Either thus or "thou makest sure," after an example in Xenophon quoted by Wettstein (ποιειν πιστα) and parallel to καινα ποιεω in Re 21:5. But it is not certain.

In whatsoever thou doest (ο εαν εργαση). Indefinite relative with modal εαν (=αν) and the first aorist middle subjunctive of εργαζομα. See Col 3:23 for both ποιεω and εργαζομα in the same sentence.

And strangers withal (κα τουτο ξενους). "And that too" (accusative of general reference as in 1 Corinthians 6:6; Ephesians 2:8). This praise of hospitality (Romans 12:13; 1 Peter 4:9; 1 Timothy 3:2; 1 Timothy 5:10; Titus 1:8; Hebrews 13:2) shows that in 2 John 1:10 John has a peculiar case in mind.