By what way is the light parted - The reference here is to the light of the morning, that seems to come from one point, and to spread itself at once over the whole earth. It seems to be collected in the east, or, as it were, condensed or concentrated there, and then to divide itself, and to expand over the face of the world. God here asks Job whether he could explain this, or show in what manner it was done. This was one of the subjects which might be supposed early to excite inquiry, and is one which can be as little explained now as then. The causes of the propagation of light, which seems to proceed from a center and to spread rapidly in every direction, are perhaps as little known now as they were in the time of Job. Philosophy has done little to explain this, and the mode in which light is made to travel in eight minutes from the sun to the earth - a distance of ninety million miles - and the manner in which it is "divided" or "parted" from that great center, and spread over the solar system, is as much of a real mystery as it was in the days of Job, and the question proposed here may be asked now with as much emphasis as it was then.
Which scattereth the east wind upon the earth - According to this translation, the idea would be that somehow light is the cause of the east wind. But it may be doubted whether this is the true interpretation, and whether it is meant to be affirmed that light has any agency in causing the wind to blow. Herder renders it:
"When doth the light divide itself,
When the east wind streweth it upon the earth?"
According to this, the idea would be that the light of the morning seemed to be borne along by the wind. Umbreit renders it, "Where is the way upon which the east wind flows forth upon the earth?" That is, the east wind, like the light, comes from a certain point, and seems to spread abroad over the world; and the question is, whether Job could explain this? This interpretation is adopted by Rosenmuller and Noyes, and seems to be demanded by the parallelism, and by the nature of the case. The cause of the rapid spreading of the wind from a certain point of the compass, was involved in as much obscurity as the propagation of the light, nor is that cause much better understood now. There is no reason to suppose that the spread of the light, has any particular agency in causing the east wind, as our common version seems to suppose, nor is that idea necessarily in the Hebrew text. The east wind is mentioned here either because the light comes from the east, and the wind from that quarter was more naturally suggested than any other, or because the east wind was remarkable for its violence. The idea that a strong east wind was somehow connected with the dawn of day or the rising of the sun, was one that prevailed, at least to some extent, among the ancients. Thus, Catullus (lxiv. 270ff) says:
Hic qualis flatu placidum mare matutino
Horrificans zephyrus proclivas incitat undas
Aurora exoriente, vagi sub lumina solis.

By what way is the light parted - Who can accurately describe the cause and operation of a thunder cloud, the cause, nature, and mode of operation of the lightning itself? Is it a simple element or compound substance? What is its velocity? and why not conductible by every kind of substance, as it is known to exist in all, and, indeed, to be diffused through every portion of nature? How is it parted? How does it take its zigzag form? this is the curious, indescribable, and unknown parting. Are all the causes of positive and negative electricity found out? What are its particles, and how do they cohere, and in what order are they propagated? Much has been said on all these points, and how little of that much satisfactorily!
Scattereth the east wind upon the earth? - קדים kadim, the eastern storm, euroclydon, or levanter.

By what way is the light parted,.... That is, dost thou know by what way it is parted or divided? as at the first creation, when God divided the light from darkness, Genesis 1:4; or at sun rising and sun setting; and so in the two hemispheres, when there is darkness on the one, and light on the other; or under the two poles, when there are interchangeably six months light and six months darkness. Or how it is parted in an unequal distribution of day and night, at different seasons and in different climates; or how on one and the same day, and at the same time, the sun shall shine in one part of the earth, and not another; and more especially if this had been now a fact, and known, that there should be darkness all over the land of Egypt, and light in Goshen. Some understand this of lightning, but that is later mentioned;
which scattereth the east wind upon the earth? that rising sometimes with the sun, or first spring of light; see Jonah 4:8; or which light spreads and diffuses itself "from the east", as it may be rendered. The sun rises in the east, and in a very quick and surprising manner spreads and diffuses its light throughout the hemisphere. Or this may respect the east wind itself, which scatters the clouds; and either spreads them in the heavens over the earth, or disperses them and drives away rain (x), as the north wind does: or as Mr. Broughton renders the words, "and the east wind scattereth itself over the earth"; it blowing invisibly and without our knowledge, goes and returns as other winds do, John 3:8.
(x) "Agente nimbos ocyor euro". Horat. Carmin. l. 2. Ode 16.

is . . . parted--parts, so as to diffuse itself over the whole earth, though seeming to come from one point. Light travels from the sun to the earth, ninety millions of miles, in eight minutes.
which scattereth--rather, "And by what way the east wind (personified) spreads (scattereth) itself." The light and east wind are associated together, as both come from one quarter, and often arise together (Jonah 4:8).

Distributed - In the air, and upon the face of the earth. This is variously distributed in the world, shining in one place and time, when it doth not shine in another, or for a longer time, or with greater brightness and power than it doth in another. All which are the effects of God's infinite wisdom and power, and such as were out of Job's reach to understand. Which - Which light scattereth, raises the east - wind, and causes it to blow hither and thither upon the earth? For as the sun is called by the poets, the father of the winds, because he draws up those exhalations which give matter to the winds, so in particular the east - wind is often observed to rise together with the sun.