Halakhah sur Les Proverbes 30:2

And Rambam, may his memory be blessed, wrote in explanation of this commandment (Guide for the Perplexed 3:48, and some have the textual variant, Ramban in his commentary to the Torah here) and of 'him and his child,' [that] it is because animals have great distress in seeing the pain of their children, like people. As the love of the mother for the child is not a matter that follows the intellect, but rather it is from the effects of the power of thinking that is found in animals, [just] as it is found in people. And Rambam, may his memory be blessed, wrote about this matter, "Do not answer me with words from the statement of the sages [in] which they say, 'To the bird's nest, etc.' since this is the reasoning of the one to whom it appears that there is no explanation for the commandments, except for them being the will of the Creator. But we maintain the second reasoning, which is that there is an explanation for all of the commandments." And [Ramban] challenged him from that which is found in Bereishit Rabbah 44a, "And for what would the Holy One, blessed be He, care if an animal is slaughtered from the [front of the] neck or from the back? Behold, the commandments were only given to refine the creatures with them, as it states (Proverbs 30:5), 'Every word of God is refined.'"