Whoso is simple, let him turn in hither - Folly or pleasure here personified, uses the very same expressions as employed by Wisdom, Proverbs 9:4. Wisdom says, "Let the simple turn in to me." No, says Folly, "Let the simple turn in to me." If he turn in to Wisdom, his folly shall be taken away and he shall become wise; if he turn in to Foliy, his darkness will be thickened, and his folly will remain.
Wisdom sets up her school to instruct the ignorant:
Folly sets her school up next door, to defeat the designs of Wisdom.
Thus the saying of the satirist appears to be verified: -
"Wherever God erects a house of prayer,
The devil surely builds a chapel there.
And it is found upon examination,
The latter has the larger congregation."
De Foe.

Whoso is simple, let him turn in hither,.... The harlot's house, Popish chapels and churches. She uses the same form of words that Wisdom does, Proverbs 9:4; having a form of godliness, a show of religion, but without the power of it; her priests are wolves in sheep's clothing, and speak lies in hypocrisy: and such that she fixes upon as proper persons to work on are the simple, the credulous and unwary; who are not on their guard, and are easily persuaded and imposed on;
and as for him that wanteth understanding; is not well grounded in the principles of Christianity he professes; has not a spiritual and experimental understanding of them:
she saith to him; addresses him in such language as follows:

The woman, who in her own person serves as a sign to her house, addresses those who pass by in their innocence (לתמּם, 2-Samuel 15:11):
16 "Whoso is simple, let him turn in hither!"
And if any one is devoid of understanding, she saith to him:
17 "Stolen waters taste sweet,
And the bread of secrecy is pleasant."
פּתי (folly, simplicity) has a side accessible to good and its contrary: Wisdom is connected with the one side, and Folly with the other. And as the חסר־לב offers a vacuum to Wisdom which may perhaps be filled with the right contents, so is this vacuum welcome to Folly, because it meets there no resistance. In this sense, Proverbs 9:16 is like Proverbs 9:4 (excepting the addition of a connecting and of a concluding ו: et si quis excors, tum dicit ei); the word is the same in both, but the meaning, according to the two speakers, is different. That to which they both invite is the pleasure of her fellowship, under the symbol of eating and drinking; in the one case it is intellectual and spiritual enjoyment, in the other sensual. That Wisdom offers (Proverbs 9:5) bread and wine, and Folly water and bread, has its reason in this, that the particular pleasure to which the latter invites is of a sensual kind; for to drink water out of his own or out of another fountain is (Proverbs 3:15-20) the symbol of intercourse in married life, or of intercourse between the unmarried, particularly of adulterous intercourse. מים גּנוּבים (correct texts have it thus, without the Makkeph) is sexual intercourse which is stolen from him who has a right thereto, thus carnal intercourse with אושׁת אישׁ; and לחם סתרים fleshly lust, which, because it is contrary to the law, must seek (cf. furtum, secret love intrigue) concealment (סתרים, extensive plur., as מעמקּים; Bttcher, 694). Just such pleasure, after which one wipes his mouth as if he had done nothing (Proverbs 30:20), is for men who are without wisdom sweet (מתק, Job 20:12) and pleasant; the prohibition of it gives to such pleasure attraction, and the secrecy adds seasoning; and just such enjoyments the כסילות, personified carnality, offers. But woe to him who, befooled, enters her house!

Simple - This title is not given them by her, but by Solomon.