After these things the word of Hashem came to Avram in a vision, saying: Fear not, Avram, I am a shield to you; your reward shall be very great.
Rashi / Bereishis Rabbah
English: After these things — after this miracle that he slew the kings, and he was anxious: perhaps I have already received the reward for all my righteousness; perhaps there was a righteous person among those I killed. Therefore He said to him: Fear not — I am a shield for you against punishment; your reward is very great.
Supplementary classical material not listed by Torah Temimah under this exact passuk.