Sforno on Genesis 29:18/ספורנו על בראשית כ״ט:י״ח

1אעבדך שבע שנים ברחל, there can be no question that a righteous man such as Yaakov would not have the audacity to marry a woman and to found a family unless he were able to support her and to provide her with the requirements specified in Exodus 21,10 as spelled out in Yevamot 19. “a man is allowed to marry several wives provided he can look after them financially.” There is therefore no reason to believe that Lavan, who was himself a man of means, would give his daughters to sons-in-law who were unable to provide for them in the manner they had been accustomed to. If all this is so, how do we explain Yaakov’s referring to the time when he crossed the river Yabbok on his way to his uncle as having only his walking staff? (Genesis 32,10)? What Yaakov meant when he said this was that at the time he referred to he had not owned any livestock, nor any profession with which to earn his livelihood. The reason he offered to work for Lavan for 7 years was to use his work in lieu of a cash dowry he would pay her father for her hand in marriage, something that was customary in those days. Lavan’s daughters themselves referred to their father having sold them into marriage in Genesis 31,15. They were modest enough to know that Lavan had taken advantage of Yaakov by demanding an exorbitantly huge amount as dowry from him. We know also from Exodus 22,16 that a father used his daughter as a source of augmenting his income and when the value of such “merchandise” had been reduced through rape or seduction of the daughter (loss of virginity) he is entitled to financial compensation by the man who seduced his daughter (when he refuses to give her to the seducer in marriage in exchange for a regular dowry).

2בתך הקטנה, although she was very young at this time, within the seven years of Yaakov’s service for her she would mature and be able to be a wife for him in the full meaning of the word.