The murderer - One of the instances, referred to in the previous verse, of those who perform their deeds in darkness.
Rising with the light - Hebrew לאור lā'ôr. Vulgate "Mane primo - in the earliest twilight." The meaning is, that he does it very early; by daybreak. It is not in open day, but at the earliest dawn.
Killeth the poor and needy - Those who are so poor and needy that they are obliged to rise early and go forth to their toil. There is a double aggravation - the crime of murder itself, and the fact that it is committed on those who are under a necessity of going forth at that early hour to their labor.
And in the night is as a thief - The same man. Theft is usually committed under cover of the night. The idea of Job is, that though these crimes cannot escape the notice of God, yet that he does not interpose to punish those who committed them. A striking incidental illustration of the fact stated here, occurred in the journey of Messrs. Robinson and Smith, on their way from Akabah to Jerusalem. After retiring to rest one night, they were aroused by a sudden noise; and they apprehended attack by robbers. "Our Arabs," says Dr. R. "were evidently alarmed. They said, if thieves, "they would steal upon us at midnight; if robbers they would come down upon towards morning." Bibl. Research. i. 270. It would seem, therefore, that there was some settled time or order in which they are accustomed to commit their various depredations.

The murderer rising with the light - Perhaps the words should be read as Mr. Good has done: -
With the daylight ariseth the murderer;
Poor and needy, he sheddeth blood.
This description is suitable to a highwayman; one who robs in daylight, and who has been impelled by poverty and distress to use this most unlawful and perilous mode to get bread; and for fear of being discovered or taken, commits murder, and thus adds crime to crime.
In the night is as a thief - Having been a highwayman in the daytime, he turns footpad or housebreaker by night; and thus goes on from sin to sin. There have been several instances like the case above, where poverty and distress have induced a man to go to the highway and rob, to repair the ruin of himself and family. I shall introduce an authentic story of this kind, which the reader may find at the end of this chapter.

The murderer rising with the light,.... The light of the morning, before the sun is risen, about the time the early traveller is set out on his journey, and men go to distant markets to buy and sell goods, and the poor labourer goes forth to his work; then is the time for one that is used to commit robbery and murder to rise from his bed, or from his lurking place, in a cave or a thicket, where he has lain all night, in order to meet with the above persons: and so
killeth the poor and needy; takes away from them the little they have, whether money or provisions, and kills them because they have no more, and that they may not be evidence against him; it may be meant of the poor saints and people of God, whom the wicked slay out of hatred to them:
and in the night is as a thief; kills privately, secretly, at an unawares, as the thief does his work; or the "as" here is not a note of similitude or likeness, but of reality and truth; and so Mr. Broughton renders the words, "and in the night he will be as a thief"; in the morning he is a robber on the highway, and a murderer; all the day he is in his lurking place, in some haunt or another, sleeping or carousing; and when the night comes on, then he acts the part of a thief; in the morning he not only robs, but murders, that he may not be detected; at night he only steals, and not kills, because men are asleep, and see him not.

with the light--at early dawn, while still dark, when the traveller in the East usually sets out, and the poor laborer to his work; the murderous robber lies in wait then (Psalm 10:8).
is as a thief--Thieves in the East steal while men sleep at night; robbers murder at early dawn. The same man who steals at night, when light dawns not only robs, but murders to escape detection.

Poor - Where he finds nothing to satisfy his covetousness, he exercises his cruelty.