When he made a decree for the rain - A statute or law (חק chôq) by which the rain is regulated. It is not sent by chance or hap-hazard. It is under the operation of regular and settled laws. We cannot suppose that those laws were understood in the time of Job, but the fact might be understood that the rain was regulated by laws, and that fact would show that God was qualified to impart wisdom. His kingdom was a kingdom of settled law and not of chance or caprice, and if the rain was regulated by statute, it was fair to presume that he did not deal with his people by chance, and that afflictions were not sent without rule; compare the notes at Job 5:6.
And a way - A path through which the rapid lightning should pass - referring, perhaps, to the apparent “opening” in the clouds in which the lightning seems to move along.
The lightning of the thunder - The word “lightning” here (חזיז chăzı̂yz) properly means “an arrow,” from הזז hāzaz, obsolete, to pierce through, to transfix, to performate; and hence, the lightning - from the rapidity with which it passes - like an arrow. The word “thunder” (קולות qôlôt) means voices, and hence, “thunder,” as being by way of eminence the voice of God; compare Psalms 29:3-5. The whole expression here means “the thunder-flash.” Coverdale renders this, “when he gave the mighty floods a law;” but it undoubtedly refers to the thunderstorm, and the idea is, that he who controls the rapid lightning, regulating its laws and directing its path through the heavens, is qualified to communicate truth to people, and can explain the great principles on which his government is administered.