Navel - The central region of the body is taken as the representative of all the vital organs. For "health" we should read healing, or, as in the marg. There is probably a reference to the local applications used by the surgery of the period as means of healing.

It shall be health to thy navel - We need not puzzle ourselves to find out what we may suppose to be a more delicate meaning for the original word שר shor than navel; for I am satisfied a more proper cannot be found. It is well known that it is by the umbilical cord that the fetus receives its nourishment all the time it is in the womb of the mother. It receives nothing by the mouth, nor by any other means: by this alone all nourishment is received, and the circulation of the blood kept up. When, therefore, the wise man says, that "trusting in the Lord with the whole heart, and acknowledging him in all a man's ways, etc., shall be health to the navel, and marrow to the bones;" he in effect says, that this is as essential to the life of God in the soul of man, and to the continual growth in grace, as the umbilical cord is to the life and growth of the fetus in the womb. Without the latter, no human being could ever exist or be born; without the former, no true religion can ever be found. Trust or faith in God is as necessary to derive grace from him to nourish the soul, and cause it to grow up unto eternal life, as the navel string or umbilical cord is to the human being in the first stage of its existence. I need not push this illustration farther: the good sense of the reader will supply what he knows. I might add much on the subject.
And marrow to thy bones - This metaphor is not less proper than the preceding. All the larger bones of the body have either a large cavity, or they are spongious, and full of little cells: in both the one and the other the oleaginous substance, called marrow, is contained in proper vesicles, like the fat. In the larger bones, the fine oil, by the gentle heat of the body, is exhaled through the pores of its small vesicles, and enters some narrow passages which lead to certain fine canals excavated in the substance of the bone, that the marrow may supply the fibres of the bones, and render them less liable to break. Blood-vessels also penetrate the bones to supply this marrow and this blood; and consequently the marrow is supplied in the infant by means of the umbilical cord. From the marrow diffused, as mentioned above, through the bones, they derive their solidity and strength. A simple experiment will cast considerable light on the use of the marrow to the bones: - Calcine a bone, so as to destroy all the marrow from the cells, you will find it exceedingly brittle. Immerse the same bone in oil so that the cells may be all replenished, which will be done in a few minutes; and the bone reacquires a considerable measure of its solidity and strength; and would acquire the whole, if the marrow could be extracted without otherwise injuring the texture of the bone. After the calcination, the bone may be reduced to powder by the hand; after the impregnation with the oil, it becomes hard, compact, and strong. What the marrow is to the support and strength of the bones, and the bones to the support and strength of the body; that, faith in God, is to the support, strength, energy, and salvation of the soul. Behold, then, the force and elegance of the wise man's metaphor. Some have rendered the last clause, a lotion for the bones. What is this? How are the bones washed? What a pitiful destruction of a most beautiful metaphor!

It shall be health to thy (e) navel, and marrow to thy bones.
(e) By this part he comprehends the whole body, as by health he means all the benefits promised in the law both corporal and spiritual.

It shall be health to thy navel,.... That part of the body which is the knot of the intestines; and may be put for the bowels and inward parts, which being sound, the body is in health; and these may be put for the whole body: and so the Septuagint version renders it, "to thy body"; and this may be put for the whole person. And the sense is, either wisdom, as Jarchi; the doctrine of wisdom, the Gospel; which teaches men to trust in the Lord, and not in themselves, to apply to him for wisdom, and not lean to their own understanding; this contributes much to a man's spiritual health and welfare: or else the fear of the Lord is of this use to men, both in soul and body; since by it they depart from those sins which bring diseases upon the body; and are influenced by it to the exercise of such graces, and the discharge of such duties, as are the means of keeping the soul in good plight;
and marrow to thy bones; or, "watering" (m) to them: that which irrigates and moistens them, and makes and keeps them strong and solid: see Job 21:24. What marrow is to the bones, that is wisdom, or the fear of God, to the souls of men; the means of establishing and strengthening them against sin, and snares and temptations, and to do the will and work of God.
(m) "irrigatio", V. L. Montanus, Tigurine version, Vatablus, Junius & Tremellius, Piscator, Cocceius, Amama, Schultens.

It--This conduct.
health--(Compare Margin).
to thy navel--for all the organs of nourishment.
marrow--(Compare Margin).
bones--frame of body. True piety promotes bodily health.

The subject to תּהי; (it shall be) is just this religious-moral conduct. The conjectural reading לבשׂרך (Clericus), לשׁרך = לשׁארך (Ewald, Hitzig), to thy flesh or body, is unnecessary; the lxx and Syr. so translating, generalize the expression, which is not according to their taste. שׁר, from שׁרר, Arab. sarr, to be fast, to bind fast, properly, the umbilical cord (which the Arabs call surr, whence the denom. sarra, to cut off the umbilical cord of the newborn); thus the navel, the origin of which coincides with the independent individual existence of the new-born, and is as the firm centre (cf. Arab. saryr, foundation, basis, Job, p. 487) of the existence of the body. The system of punctuation does not, as a rule, permit the doubling of ר, probably on account of the prevailing half guttural, i.e., the uvular utterance of this sound by the men of Tiberias.
(Note: See my work, Physiologie u. Musik in ihrer Bedeutung fr Grammatik besonders die hebrische, pp. 11-13.)
לשׁרּך here, and שׁרּך at Ezekiel 16:4, belong to the exceptions; cf. the expanded duplication in שׁררך, Song 7:3, to which a chief form שׁרר is as little to be assumed as is a הרר to הררי. The ἅπ. γεγρ. רפאוּת, healing, has here, as מרפּא, Proverbs 4:22; Proverbs 16:24, and תּרוּפה, Ezekiel 47:12, not the meaning of restoration from sickness, but the raising up of enfeebled strength, or the confirming of that which exists; the navel comes into view as the middle point of the vis vitalis. שׁקּוּי is a Piel formation, corresponding to the abstract Kal formation רפאוּת; the Arab. saqâ, used transit. (to give to drink), also saqqâ (cf. Pu. Job 21:24) and asqâ, like the Hebr. השׁקה (Hiph. of שׁקה, to drink); the infin. (Arab.) saqy means, to the obliterating of the proper signification, distribution, benefaction, showing friendship, but in the passage before us is to be explained after Job 21:24 (the marrow of his bones is well watered; Arnheim - full of sap) and Proverbs 15:30. Bertheau and Hitzig erroneously regard Proverbs 3:8 as the conclusion to Proverbs 3:7, for they interpret רפאות as the subject; but had the poet wished to be so understood, he should have written וּתהי. Much rather the subject is devotion withdrawn from the evil one and turned to God, which externally proves itself by the dedication to Him of earthly possessions.

Navel - To thy body, which is signified by one part of it. Marrow - Which is the nourishment and strength of the bones.