Genesis 30:3 - Coke's Commentary on the Holy Bible

Behold my maid, &c.— Struck with the force of her husband's reproof, she bethought herself of the usual way, at that time, for women in her case to become mothers: to which end she gave Bilhah her handmaid to Jacob, as Sarah had done heretofore to Abraham. And she shall bear upon my knees, said Rachel; which the Chaldee paraphrases, and I shall be a nurse, which appears to be the true meaning of the phrase, and in which sense it might be rendered more properly she shall bear for my knees; a sense which על (al) is often used in, as may be seen in Noldius. So ch. Genesis 50:23. it is said, that the children of Machir were brought up (Heb. born) upon or for Joseph's knees. The children of the handmaids were esteemed the children of the wife, as we have before observed. So Rachel designed that Bilhah should bear children, which she would bring up and dandle on her knees as her own children, that thus she might be built up, or have a family through her. See Parker's 34th Occasion. Annotation.