The Greek word chrēstotēs — translated "kindness" or "gentleness" in the New Testament — shares a root with the word for what is good and useful. It is not softness for its own sake; it is active goodness directed toward someone's actual need. Paul lists it in the fruit of the Spirit in Galatians 5 and as something God clothes his elect in through Colossians 3. In both cases, it is not optional ornamentation; it is the character of people who have been changed by the Spirit.
Titus 3:4 uses this word directly of God: "But after that the kindness and love of God our Saviour toward man appeared." The incarnation is described as an appearance of kindness. What came in Jesus was not primarily judgment or law but chrēstotēs — the goodness of God reaching toward people who could not reach God. Human kindness is downstream from that event.
Proverbs 31:26 says of the virtuous woman that "in her tongue is the law of kindness." The law — Torah — of kindness. Her speech has a governing principle, not just a pleasant tone. She doesn't just happen to be kind when the mood strikes; she is structured around it. Kindness as a governing law of speech is an unusual standard — it asks about the pattern, not just the exceptional moments.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.