Adam Clarke on Psalms 52:6

The righteous also shall see, and fear - The thing shall be done in the sight of the saints; they shall see God's judgments on the workers of iniquity; and they shall fear a God so holy and just, and feel the necessity of being doubly on their guard lest they fall into the same condemnation. But instead of וייראו veyirau, "and they shall fear," three of Kennicott's and De Rossi's MSS., with the Syriac, have וישמחו veyismachu, "and shall rejoice;" and, from the following words, "and shall laugh at him," this appears to be the true reading, for laughing may be either the consequence or accompaniment of rejoicing.