Adam Clarke on Ecclesiastes 7:20

There is not a just man upon earth, that doeth good, and sinneth not - לא יחטא lo yechta, that may not sin. There is not a man upon earth, however just he may be, and habituated to do good, but is peccable - liable to commit sin; and therefore should continually watch and pray, and depend upon the Lord. But the text does not say, the just man does commit sin, but simply that he may sin; and so our translators have rendered it in 1Sam 2:25, twice in 1Kgs 8:31, 1Kgs 8:46, and 2Chr 6:36; and the reader is requested to consult the note on 1Kgs 8:46, where the proper construction of this word may be found, and the doctrine in question is fully considered.