The Chatam Sofer writes that the small kaf seems to hint at what is found in the Gemara (Bava Batra 16b) with regards to the Pasuk: אֶת־אַבְ רָ הָם בַּכּ ֹל בֵּרַ ך וה' – Hashem blessed Avraham with everything. The Gemara presents an opinion that Avraham had a daughter named "בַּכּ ֹל" but she died. As long as Sarah was alive, he did not feel the lack of his daughter so much, because he was not alone, and he was also comforted by Sarah. But when Sarah also died and he was left alone, he began to feel the bitterness and also weep for the death of his daughter. He states that it is known that small letters in the Torah indicate deficiency and a lack of something, and if you remove the kaf from תָ הּ כּ ֹ וְלִבְ, it reads וּלְבִ תָּ הּ – and for his daughter, hinting that Avraham came to eulogize Sarah and to weep for her and for his daughter.
