When he slew them, then they sought him. By the circumstance here recorded, it is intended to aggravate their guilt. When under a conviction of their wickedness they acknowledged that they were justly punished, and yet did not with sincerity of heart humble themselves before God, but rather mocked him, intending to put him off with false pretences, their impiety was the less excusable. If a man who has lost his judgment does not feel his own calamities, he is excusable because he is insensible; but he who is forced to acknowledge that he is culpable, and yet always continues the same, or after having lightly sought pardon, in fair but deceitful words, suddenly returns to his former state of mind, manifestly shows by such hollowness of heart that his disease is incurable. It is here tacitly intimated, that the punishments, by which a people so obstinate were constrained to seek God, were of no common or ordinary kind; and we are informed, (verse 35, [1]) not only that they were convinced of wickedness, but also that they were affected with a sense and a remembrance of the redemption from which they were fallen. By this means they are the more effectually deprived of all excuse on the ground of ignorance. The language implies that they were not carried away inadvertently, or deceived through ignorance, but that they had provoked the wrath of God, by dealing treacherously, as it were with deliberate purpose. And, indeed, God opened their eyes with the view of more openly discovering their desperate wickedness, as if, shaking off their hypocrisy and flatteries, he drew them from their lurking-places into the light.

Footnotes

1 - In the Hebrew Bible, a masoretic note is inserted after the 35th verse, chtsy hsphr, chatsi ha-sepher, the middle of the book, that is, with respect to verses.

When he slew them - When he came forth in his wrath and cut them down by the plague, by fiery serpents, or by their enemies.
Then they sought him - Their calamities had the effect of producing temporary reformation. They became professedly penitent; they manifested a wish to know God, and expressed a purpose to serve him. It was, however, a temporary and hollow, not a deep and real reformation. This often occurs. In times of affliction, in sickness, in bereavement, in the loss of property, people become serious, and express a purpose to repent and turn to God. A deep impression seems to be produced on their minds, to last, alas! only as long as the hand of God rests upon them. Resolutions of repentance are formed only to be forgotten when the affliction is removed, and when the days of prosperity again return.
And they returned and inquired early after God - The word rendered "inquired early" has reference to the first rays of the morning - the aurora - the dawn. Then it comes to denote the beginning of anything; or, the first thing. Thus employed, it may refer to the act of seeking God as the first thing; in youth; in the morning; at the commencement of any enterprise or undertaking. See Proverbs 8:17; Proverbs 1:28. Here it means that, in their affliction, they did not delay to seek God, but expressed an early intention of serving him. They evinced a prompt purpose to break off their sins, and to return to him.

When he slew them - While his judgments were upon them, then they began to humble themselves, and deprecate his wrath. When they saw some fall, the rest began to tremble.

When he (t) slew them, then they sought him: and they returned and enquired early after God.
(t) Such was their hypocrisy, that they sought God out of fear of punishment, though in their heart they did not love him.

When he slew them,.... Some of them, the spies particularly; or when he threatened to slay them, or was about to do it:
then they sought him; that is, those who either survived the slain, or were threatened with destruction; these sought the Lord by prayer and supplication, that he would not destroy them; the Targum is,
"they repented and sought him;''
see Numbers 14:37,
and they returned; from their evil ways, and by repentance, at least in show and appearance:
and inquired early after God; but not earnestly, and with their whole hearts and spirits; the Targum is,
"they prayed before God;''
which is often done, by carnal professors, in trouble; see Isaiah 26:16, Hosea 5:15.

Returned - From their idols. Enquired - Speedily sought to God for ease and safety.