Charles Ellicott Commentary Psalms 31:21

"Blessed be Jehovah; For he hath showed me his marvellous lovingkindness in a strong city." — Psalms 31:21 (ASV)

Showed me his marvelous kindness ... —Better, made his kindness distinguished or manifest, referring to Psalms 31:19.

In a strong city. —Some see a reference to David’s adventures at Ziklag or Keilah; others to Jeremiah’s in Jerusalem (Jeremiah 38:0). It is, however, better to regard it merely as a general image of the Divine protection.