Here the discussion explains why Abraham and Isaac replied as above when they were asked about their wives. This episode is linked to the Shechinah, the Divine Presence of Creator in the physical realm. The dual meaning of the word sister is revealed as an allusion to the patriarchs' own connection to the Shechinah, which is the source of human happiness and protection. The Rabbis further discuss the nature and whereabouts of the dwelling place of the Shechinah, which resides both in their wives and in the Holy Land.
The Shechinah can only dwell within us, offering protection and fulfillment, when we are in an appreciative and joyful state of mind. The moment a person feels depressed, negative, or victimized, the Shechinah departs. A positive state of mind and appreciation is summoned forth in this passage, thus drawing the Shechinah into our lives. This Light also serves to enrich our marital relationships.