John Gill Commentary Ecclesiastes 7:27

"Behold, this have I found, saith the Preacher, [laying] one thing to another, to find out the account;" — Ecclesiastes 7:27 (ASV)

Behold, this have I found
That a harlot is more bitter than death; and which he found by his own experience, and therefore would have it observed by others for their caution:

or one man among a thousand, (Ecclesiastes 7:28) ; (says the preacher) ;
of which title and character see (Ecclesiastes 1:1) ; it is here mentioned to confirm the truth of what he said; he said it as a preacher, and, upon the word of a preacher, it was true; as also to signify his repentance for his sin, who was now the "gathered soul", as some render it; gathered into the church of God by repentance;

[counting] one by one, to find out the account ;
not his own sins, which he endeavoured to reckon up, and find out the general account of them, which yet he could not do; nor the good works of the righteous, and the sins of the wicked, which are numbered before the Lord one by one, till they are added to the great account; as Jarchi, from the Rabbins, interprets it, and so the Midrash: but rather the sense is, examining women, one by one, all within the verge of his acquaintance; particularly the thousand women that were either his wives or concubines; in order to take and give a just estimate of their character and actions. What follows is the result.