23:6 Do not eat the food of a stingy person,
do not crave his delicacies;
23:7 for he is like someone calculating the cost in his mind.
“Eat and drink,” he says to you,
but his heart is not with you;
23:8 you will vomit up the little bit you have eaten,
and will have wasted your pleasant words.

We might well agree that the meaning of this proverb is accurately summarised by the Faithlife Study Bible:

‘This proverb warns against eating with a stingy person. The stingy person may appear hospitable and generous on the outside but is resentful and calculating inside.’

However, verses 6-8 read in the AV:-

6  Eat thou not the bread of him that hath an evil eye,
Neither desire thou his ddainty meats:
7  For as he thinketh in his heart, so is he:
Eat and drink, saith he to thee;
But his heart is not with thee.
8  The morsel which thou hast eaten shalt thou vomit up,
And lose thy sweet words.

There is a tradition of quoting the highlighted part of v7 in the form,

‘As a man thinketh, so is he’.

In this form, it has become a goto verse for purveyors of ‘positive thinking’.

Here are a few examples from popular (i.e. non-academic) sources.  All take their ‘inspiration’ from Prov 23:7, in the form just quoted:

‘Train your mind to see beyond the present circumstances and embrace your glorious future even before you step into it.’ (Source)

‘Train your mind to think positively. If you keep repeating negative thoughts,you eventually become them. Your mind is that powerful.’ (Source)

‘So we become what we think about most of the time. Our thoughts can have a POWERFUL influence in our lives. What are we thinking right now. Monday sucks? Or this Monday will be full of great surprises and blessings? Either way, it will be so. Let’s think success and not defeat. WE HAVE MORE POWER THAN WE THINK!! Have an AMAZING MONDAY!’ (Source)

Such a (mis)interpretation and (mis)application of this verse is not the exclusive property of ‘prosperity’ teachers, however.  The following comes from respected Reformed source:

‘The longer one lives in this world as a Christian, the more he or she becomes aware of the significance of their words and thoughts. The mind of the the believer plays a far more central role than we often realise. ‘As a man thinketh in his heart, so is he’, the scriptures say. We realise more and more that the battle in the Christian life really is a battle for the mind to be renewed and controlled by God’s truth. As a person ‘thinketh’ in their heart, so they are and so they will be.’ (Source)

Compare this:

‘“As [a man] thinketh in his heart, so is he” (Proverbs 23:7 KJV). What a man thinks in his heart — not what he says with his mouth — is where to find the man naked in his natural habitat. He may say warmly enough to be convincing, “Sit, eat, and drink,” but sweet words can coat a bitter heart. He may brood against you while he bids you to his table. What he thinks inwardly, his soliloquy uttered in secret chambers — that is the man as he is.

‘But we may go further: “As a man thinketh in his heart, so he will become.” That man in the inner chamber may change — for better or worse — depending on where he sets his innermost thoughts. Beautiful or beastly, peaceful or disturbed, heavenly or hellish — as a man thinketh in his heart, so he will become.’ (Source)

Slightly more relevant to the text are the following comments by Matthew Henry and John Kitchen (Mentor):

Henry:

‘We are that really, both to God and man, which we are inwardly; and neither religion nor friendship is worth any thing further than as it is sincere.’

Kitchen:

‘it is not what he says or how he behaves outwardly that determines who he truly is. Rather, it is what he is thinking within himself as you eat of his food and partake of his drink that defines the reality of his character.’

But, insofar as the above readings disregard the context, they ignore the main point of the proverb.

In context, the theme of the proverb is the heart of a stingy host.  The following captures the sense well:

‘Craving such a man’s delicacies is dangerous because his generosity is false. With a warm welcome, he says, “Eat and drink,” but his heart is not in it. He’s not glad to see you enjoying his fare; rather, he is watching every bite you take and calculating the cost the whole time. Once you realize what your host is thinking, you’ll want to spit out your food because what seemed to be offered so freely was begrudgingly served. And all of your kind compliments and table talk was wasted. The penny-pinching host was not genuinely interested in sharing his bounty with you or listening to the conversation you shared as his guest. Everything you said fell on deaf ears, because he is the kind of man who is always “thinking/calculating in his heart.”’ (Source)

This is clear enough in the older translations.

The RV, for example, continues the tradition of the AV:

6 Eat thou not the bread of him that hath an evil eye,
Neither desire thou his dainties:
7 For as he reckoneth within himself, so is he:
Eat and drink, saith he to thee;
But his heart is not with thee.
8 The morsel which thou hast eaten shalt thou vomit up,
And lose thy sweet words.

So also the NKJV:

6 Do not eat the bread of a miser,
Nor desire his delicacies;
7 For as he thinks in his heart, so is he.
“Eat and drink!” he says to you,
But his heart is not with you.
8 The morsel you have eaten, you will vomit up,
And waste your pleasant words.

They main point of the proverb becomes even clearer as we move into modern translations.

RSV:

6 Do not eat the bread of a man who is stingy;
do not desire his delicacies;
7 for he is like one who is inwardly reckoning.
“Eat and drink!” he says to you;
but his heart is not with you.
8 You will vomit up the morsels which you have eaten,
and waste your pleasant words.

NET:

23:6 Do not eat the food of a stingy person,
do not crave his delicacies;
23:7 for he is like someone calculating the cost in his mind.
“Eat and drink,” he says to you,
but his heart is not with you;
23:8 you will vomit up the little bit you have eaten,
and will have wasted your pleasant words.

ESV:

6  Do not eat the bread of a man who is stingy;
do not desire his delicacies,
7  for he is like one who is inwardly calculating.
“Eat and drink!” he says to you,
but his heart is not with you.
8  You will vomit up the morsels that you have eaten,
and waste your pleasant words.

One slight outlier from this modern consensus is the NRSV, which in v7 introduces a translation which is based on the LXX:

6 Do not eat the bread of the stingy;
do not desire their delicacies;
7 for like a hair in the throat, so are they.
“Eat and drink!” they say to you;
but they do not mean it.
8 You will vomit up the little you have eaten,
and you will waste your pleasant words.

Among the commentators, even the older writers often agree that, in context, the main point is

‘He estimates his meats, and the cost of the entertainment, more than he does you; and is ill at ease if you eat much of his food.’ (JFB)

Modern commentators achieve a near-consensus.

Kidner:

‘It takes away the relish (8)…to have one’s grudging host (evil eye, AV, RV: cf. 22:9; Matt. 20:15) doing mental arithmetic (7a) with each dish.’

Waltke:

‘Outwardly the host conforms to his social obligation according to Oriental rules of hospitality but inwardly he is revolted by his guest.’

According to Murphy (UBOT) vv 6-8 constitute:

‘An admonition not to dine with a miserly host.’

Murphy (WBC): The hypocrisy of the host is revealed by the contrast between his thoughts and his words.

Fox (AYB):

‘While he invites you to eat, he is silently calculating costs and benefits. He is brooding on the cost of every bite you take and wondering if you are worth it.’