Confidence in an unfaithful man in time of trouble is like a broken tooth, and a foot out of joint.

To trust to an unfaithful man in the time of trouble, is like a rotten tooth, and weary foot,

A broken tooth, and a tottering foot, is confidence in an unfaithful man in the day of trouble.

A bad tooth, and a tottering foot, Is the confidence of the treacherous in a day of adversity.

Putting one's faith in a false man in time of trouble is like a broken tooth and a shaking foot.

Whoever sets his hopes on the unfaithful in a day of anguish is like a rotten tooth and weary foot,

Stress is to be laid on the uselessness of the "broken tooth" and the "foot out of joint," or tottering, rather than on the pain connected with them. The King James Version loses the emphasis and point of the Hebrew by inverting the original order, which is "a broken joint is confidence" etc.

Confidence in an unfaithful man in time of trouble,.... It is not good to put confidence in any man, not in princes, nor in the best of men; much less in an unfaithful, prevaricating, and treacherous man; and especially in a time of distress and trouble, depending on his help and assistance, which is leaning on a broken reed, and trusting to a broken staff. Or, "the confidence of an unfaithful man in time of trouble" (o); that which he puts confidence in; who trusts in his riches, or in his righteousness, or in his own heart, all which are vain and deceitful:
is like a broken tooth, and a foot out of joint; which are so far from being of any use, the one in eating food, and the other in walking, that they are both an hindrance to those actions, and cause pain and uneasiness: or, "a bad tooth", so the Targum and Syriac version; a rotten one.
(o) "fiducia praevaricatoris", Pagninus, Montanus, Mercerus, Gejerus; "fiducia perfidi", Cocceius, Michaelis.

Confidence in an unfaithful man is painful and vexatious; when we put any stress on him, he not only fails, but makes us feel for it.

Treachery annoys as well as deceives.

19 A worthless tooth and an unsteady foot -
Trust in a faithless man in the day of need.
The form רעה (with Mercha on the antepenult), Isaiah 29:19, takes the place of an inf. absol.; רעה here (about the tone syllable of which Dech does not decide, thus without doubt Milra) is certainly not a subst.: tooth of breaking (Gesen.); for how strange such a designation of a worthless tooth! שׁן is indeed mas. in 1-Samuel 14:5, but it can also be used as fem., as רגל, which is for the most part fem., also occurs as mas., Gttche. 650. Bttcher, in the new Aehrenlese, and in the Lehrbuch, takes רעה as fem. of an adj. רע, after the form חל; but חל is not an adj., and does not form a fem., although it means not merely profanity, but that which is profane; this is true also of the Aram. חוּל; for חוּלתּא, Esther 2:9, Targ., is a female name mistaken by Buxtorf. Are we then to read רעה, with Hitzig, after the lxx? - an unimportant change. We interpret the traditional רעה, with Fleischer, as derived from רועעה, from רועע, breaking to pieces (crumbling), in an intransitive sense. The form מוּעדת is also difficult. Bttcher regards it as also, e.g., Aben Ezra after the example of Gecatilia as part. Kal. = מועדת, "only on account of the pausal tone and the combination of the two letters מע with instead of ." But this vocal change, with its reasons, is merely imaginary. מוּעדת is the part. Pual, with the preformative מ struck out, Ewald 169d. The objection that the part. Pual should be ממעד, after the form מבער, does not prove anything to the contrary; for מועדת cannot be the fem. so as not to coincide with the fem. of the part. Kal, cf. besides to the long the form without the Dagesh יוּקשׁים, Ecclesiastes 9:12 = מיקּשׁים (Arnheim, Gramm. p. 139). רגל מוּעדת is a leg that has become tottering, trembling. He who in a time of need makes a faithless man his ground of confidence, is like one who seeks to bite with a broken tooth, and which he finally crushes, and one who supports himself on a shaking leg, and thus stumbles and falls. The gen. connection מבטח בוגד signifies either the ground of confidence consisting in a faithless man, or the confidence placed in one who is faithless. But, after the Masora, we are to read here, as at Psalm 65:6, מבטח, which Michlol 184a also confirms, and as it is also found in the Venice 1525, Basel 1619, and in Norzi. This מבטה is constr. according to Kimchi, notwithstanding the Kametz; as also משׁקל, Ezra 8:30 (after Abulwald, Kimchi, and Norzi). In this passage before us, מבטח בוגד may signify a deceitful ground of confidence (cf. Habakkuk 2:5), but the two other passages present a genit. connection of the words. We must thus suppose that the ā of מבטח and משׁקל, in these three passages, is regarded as fixed, like the of the form (Arab.) mif'âl.