John Calvin Commentary Genesis 30:5

"And Bilhah conceived, and bare Jacob a son." — Genesis 30:5 (ASV)

And Bilhah conceived. It is wonderful that God should have seen fit to honor an adulterous connection with offspring: but he sometimes strives in this way to overcome by kindness the wickedness of people, and pursues the unworthy with his favor. Moreover, he does not always make the punishment equal to the offenses of his people, nor does he always rouse them equally quickly from their sluggishness, but waits for the proper time of correction.

Therefore, it was his will that those who were born from this flawed union should nevertheless be counted among the legitimate children; just as Moses just before called Bilhah a wife, who, however, might more properly have been called a harlot. And the common rule does not hold that what had no validity from the beginning can never gain validity over time; for although the agreement, into which the husband and wife sinfully entered against God's command and the sacred order of nature, was void, it nevertheless came about by special privilege that the union, which in itself was adulterous, obtained the honor of marriage.

Finally, Rachel begins to attribute to God what is his own; but her confession is so mixed with ambition that it conveys nothing of sincerity or uprightness. She pompously proclaims that her cause has been undertaken by the Lord. As if, indeed, she had been so injured by her sister that she deserved to be uplifted by God's favor; and as if she had not attempted to deprive herself of his help. We see, then, that under the pretext of praising God, she rather wrongs him by making him subservient to her desires. Add to this, that she imitates hypocrites who, while in adversity, rush against God with closed eyes; yet when more prosperous fortune favors them, indulge in empty boasts, as if God smiled upon all their deeds and sayings. Rachel, therefore, does not so much celebrate the goodness of God as she applauds herself. Therefore, let the faithful, learning from her example, refrain from defiling the sacred name of God with hypocrisy.