Whenever the subject of jewish patriarchs comes up, two of the most prominant figures that come to mind are Rabinu Moshe and Avinu Avraham. For this lesson, I refer to Abraham as "mother", even though he is regarded as the father of a multitude. I am not being blasphemous, as you shall see as you read on. Let's start with Moses, who like Abraham, was not born a tzaddik but had to discover his destiny in a royal society. Moses' calling began at Mount Horeb. During the Exodus, a diaspora of sorts, the conditions of wandering for forty years were extremely harsh, not only due to natural elements, but moreso because of the demands of the Torah. Like the strict and stern father, Moses had to enforce these laws and judgements for the ultimate benefit of an exiled people. This was a time of Gevurah (judgement), and Moses was the enforcer.
Psalm 90 clearly shows that Moses lamented this aspect, but as a leader in that time and place, it was necessary. His strong temper is also apparent, and through the Exodus account we see that this may have been the great Teacher's only sin. As a human-being, even the Servant of YHVH must have a weakness !
Then we have Abraham. By traditional accounts, Abraham was most generous and merciful, rich in livestock and known for offering food to strangers, and when these strangers tried to pay, Abraham would say "sufficient to praise haShem."
Abraham pleaded for YHVH to spare Sodom, the most violent civilization in history. Like the nurturing mother, Abraham clearly represents the aspect of Chesed (mercy). This is why I say "father" Moses and "mother" Abraham, because in a common household, children are raised best with both aspects. In the Etz Chaim, the sefirot of Gevurah and Chesed balance each-other perfectly. As kabbalists, let us strive for this perfect balance.
