John Calvin Commentary Genesis 29:25

"And it came to pass in the morning that, behold, it was Leah. And he said to Laban, What is this thou hast done unto me? Did not I serve with thee for Rachel? Wherefore then hast thou beguiled me?" — Genesis 29:25 (ASV)

And he said to Laban. Jacob rightly protests the fraud committed against him. And Laban's answer, though not without some superficial justification, still offers no excuse for the fraud. It was not the custom to give younger daughters in marriage before the elder, and injustice would have been done to the firstborn by disrupting this established order.

But for that reason, he should not have deceitfully betrothed Rachel to Jacob and then substituted Leah in her place. He should rather have cautioned Jacob himself beforehand to turn his thoughts to Leah, or else to refrain from marrying either of them.

But we may learn from this that wicked and deceitful men, once they have turned aside from truth, continually transgress; meanwhile, they always offer some superficial justification to free themselves from blame. He had previously acted unjustly toward his nephew by demanding seven years’ labor for his daughter; he had also unjustly sold his daughter, without a dowry, for the sake of gain. But the most shameful act of all was treacherously to deprive his nephew of his betrothed wife, to corrupt the sacred laws of marriage, and to leave nothing safe or sound. Yet we see him pretending that he has an honorable defense for his conduct, because it was not the custom of the country to prefer the younger to the elder.