Rashi on Deuteronomy 7:7/רש"י על דברים ז׳:ז׳

1לא מרבכם NOT ON ACCOUNT OF YOUR BEING [MORE] NUMEROUS — This is to he understood according to its plain sense. But its Midrashic explanation (taking לא מרבכם in the sense of “not because you are great") is: Because you do not regard yourselves as great when I shower good, upon you, therefore חשק … בכם DID [THE LORD] DELIGHT IN YOU

2כי אתם המעט FOR YOU ARE LITTLE — you regard yourselves as small, as, e.g., Abraham did who said, (Genesis 18:27) “For I am dust and ashes", and as, e.g., Moses and Aaron did who said, (Exodus 16:7) “And we, what are we?". Not as Nebuchadnezzar who said, (Isaiah 14:14) “I will be like the Most High", and Sennacherib who said, (Isaiah 36:20) “Who are they among all the gods of these countries [that have delivered their countries out of my hand?]", and Hiram who said, (Er. 28:2), “I am a god, I sit in the seat of God" (Chullin 89a).

3כי אתם המעט — Here you have the word כי used in the sense of “because".