From the Rebbe’s explanation:
– A chazakah associated with the number three represents a concept of true strength, for this strength exists even within a situation where there are opposing forces.
As is well known, the number one refers to a state in which there exists only good and holiness.
Two, in contrast, refers to a state in which difference exists and even division and strife may arise.
Three, however, reflects the strength and power of holiness even in the face of such difference.
There are two conceptions of such a state of strength:
a) The strength results from the unlimited light of holiness. This light is so powerful, that even in the face of opposition, it can be expressed in every place.
b) The strength depends on the service of the lower realms and their efforts to negate all factors opposed to holiness and indeed, to transform them into positive forces.
Based on the Rebbe’s talk on Shabbat “Matot-Masey”, 5751 (1991).