The choicest of your first fruits you shall bring to the house of Hashem, your G-d. Do not boil a kid in its mother's milk.
The Ohr Hachaim explains this as an exhortation against wasting seed. A person should be careful that his first drop of seed, equivalent to his first fruit, should be brought to the house of Hashem. The house of Hashem is a euphemism for a person’s wife. He should not frequent harlots and waste his seed on them.
The Torah ends with a prohibition against cooking a goat in its mother’s milk. This hints at a lofty spiritual idea. Those who waste their seed cause young children to die in their mother’s arms. The possuk writes הַאֶׁתֵן בְכוֹרִׂ י פִׂשְעִׂי פְרִׂ י בִׂטְנִׂי חַטַאת נַפְשִׂ י - Shall I give my firstborn for my disobedience? The fruit of my body for the sin of my soul? Young children are collateral for the parents’ aveiros. These souls are snatched away if a person does not reserve his first seed for the house of Hashem.
Even in the simple explanation, there is a similarity between the Mitzva of Bikurim and the prohibition against eating meat and milk together. Both are not only forbidden for a person to eat, they are prohibited to derive any benefit from it. Bikurim is only for Cohanim, others may not even derive any pleasure from it. As is meat and milk cooked together.
