The beginning of the Parsha describes how childbirth renders a woman ritually impure. This may be surprising because Judaism tends to think of having children as an unparalleled act of holiness. Why would such a special and beautiful act render a woman impure?
Rabbi Norman Lamm explains that every act of creation always contains a little impurity
“The creative act involves an area of shade, something negative, an element of pain and agony and frustration. The seed must rot for the plant to grow. When you carve wood, you must expect splinters. The sculptor must chip away part of the block and discard it in order to have the figure, which his imagination has conceived, emerge.”
The Torah is teaching us this valuable lesson to teach us to always be on the lookout for impurity even when engaged in the most holy of acts. It provides a method for anticipating the negative side-effects of our actions and purifying ourselves when they occur.