A Zivug [coupling] to sustain the worlds, a Zivug that does not stop, which is covered Hassadim. A Zivug for engendering souls, a Zivug that stops, and it is considered Hochma.
On the right, it is possible to live but not to engender, but on the left, which is Hochma, called “deficiency,” it is possible to engender the next state. Conversely, one who desires mercy is content with his share and has life but not for engendering because he is happy the way he is, so why should he want a different state?
A unification (Zivug) to sustain the worlds is a continuous unification and it gives life. A unification for engendering souls is a unification that stops, meaning intermittent. We must engage in unification in both.
A corporeal example is that in order to live, we cannot say, When do we not have to live? This comes from the quality of desiring mercy, when one is content with his share. But to engender, this is something in which we do not always need to engage, since engendering a new state is specifically through a deficiency, and a person should not constantly engage in deficiencies.