בראשית פרק כד, ס וַיְבָרֲכוּ אֶׁת-רִּ בְ קָה(Blessing to Rivkah on her engagement from this verse) We learn not to mix Mitzvos together to avoid the appearance of making the Mitzvos appear to be a burden and that we wish to get rid of them quickly. This action of mixing two Mitzvos together (burden) would lessen the Torah making the appearance that each Mitzvah has no independent purpose and that no order exists within the Torah.

Blessing to Rivkah and Mixing Mitzvos