18 Here γάρ (gar) has not been translated because of differences between Greek and contemporary English style.
19 The Greek preposition ἐπί (epi) is understood here in a causal sense, i.e., “because.”
20 The word translated “hearts” here is σπλάγχνα (splanchna). Literally the term refers to one’s “inward parts,” but it is commonly used figuratively for “heart” as the seat of the emotions. See σπλάγχνον 2 (cf. Col 3:12, Phil 2:1).

In other versions

For I have derived much joy and comfort from your love, my brother, because the hearts of the saints have been refreshed through you.

Your love has given me great joy and encouragement, because you, brother, have refreshed the hearts of the Lord’s people.

For I have great joy and encouragement from your love, because the hearts of the saints have been refreshed through you, brother.

Your love has given me much joy and comfort, my brother, for your kindness has often refreshed the hearts of God’s people.

For I have great joy and encouragement from your love, because the hearts of the saints have been refreshed through you, brother.

For we have great joy and consolation in thy love, because the bowels of the saints are refreshed by thee, brother.

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