Exodus Rabbah, Mishpatim, 31:13

Another explanation of “Even to the poor with you”. The poor is not with you, but with Me. Thus, too, said David: “For You save the poor people (Psalms 18:28). The ways of God are not those of people. When one is rich and has a poor relative, one does not acknowledge the relative; for when one sees the relative, one hides, being ashamed to speak to the poor relative because they are poor. Solomon said this, “All the brothers of a poor man despise him” (Proverbs 19:7), and also “The poor is hated even by their own neighbor” (ibid 14:20); Job also said, “And my acquaintances are wholly estranged from me” (Job, 19:13). If one, however, is rich, all cleave to them and love them, as it says, “But the rich has many friends” (Proverbs 14:20). With God it is not so, for the poor are God’s people. When God sees a poor person, God cleaves to that person. A proof? Read what it says: “Thus says the Lord; the heaven is My throne” (Isaiah 66:1), and what does it say after this? “But on this person will I look, even on one who is poor and of a contrite spirit” (ibid verse 2). And so, too, spoke Moses to Israel: “The Lord did not set love upon you, nor choose you, because you were more in number than any people - for you were the fewest of all peoples (Deuteronomy 7:7). When God will favor Zion once again it will be the poor who will first receive God’s mercy, for it says, “That the Lord has founded Zion, and in her will the poor of God’s people take refuge” (Isaiah 14:32), and also, “For God has comforted God’s people, and has compassion upon God’s poor” (ibid verse 13). Hence, “Even to the poor with thee””: the poor and not with thee, but with Me, as it says “For You save the poor people.” [Soncino translation. Edited for gender neutrality and updated language]