Albert Barnes Commentary Job 29:3

"When his lamp shined upon my head, And by his light I walked through darkness;" — Job 29:3 (ASV)

When his candle shone upon my head – The margin reads, “or, lamp;” (compare the notes on Job 18:6). It was remarked in the note on that passage that it was common to have lamps or lights always burning in a house or tent. When Job speaks of the lamps shining “on his head,” the allusion is probably to the custom of suspending a lamp from the ceiling, a custom that prevails among the wealthy Arabs. “Scott.” Virgil speaks of a similar thing in the palace of Dido:

Dependent lychni laquearibus aureis Incensi.
(Aeneid 1:726.)
“From gilded roofs depending lamps display
Nocturnal beams that imitate the day.”
—Dryden

See also Lucretius 2:24. Indeed, the custom is common everywhere, and the image is a beautiful illustration of divine favor—of light and happiness imparted by God, the great source of blessedness from above.

The Hebrew word translated “shone,” בהלו (behilô), has caused some perplexity regarding its form. According to Ewald, Hebrew Grammar, p. 471, and Gesenius, Lexicon, it is the Hiphil form of הלל (hâlal) – to shine – with the He preformative dropped. The sense is, “In his causing the light to shine.” Others suppose that it is the infinitive of the Qal, with a pleonastic suffix, meaning “when it shone;” that is, the light. The sense is essentially the same; compare Schultens and Rosenmuller in loc.

And when by his light – Under his guidance and direction.

I walked through darkness – “This probably refers to the fires or other lights that were carried before caravans in their nightly travels through the deserts.” “Noyes.” The meaning is that God provided him with protection, instruction, and guidance.

In places and on subjects that would have been otherwise dark, God counseled and led him. He enjoyed the manifestations of divine favor; his understanding was enlightened, and he was enabled to comprehend subjects that would have been otherwise perplexing and difficult. He refers, probably, to the inquiries about divine government and administration, and to the questions that came before him as a magistrate or an umpire—questions that he was enabled to determine with wisdom.