Problem: God is represented in the Scriptures as someone who “is no respect[er] of persons” (Rom. 2:11, kjv), and one who “shows no partiality” (Deut. 10:17). Yet, this verse tells us that God “did not respect Cain and his offering,” which seems contradictory to the other verses.
Solution: First of all, in the fundamental sense of the word, God respects every person for who he or she is, a creature made in His image and likeness (Gen. 1:27). If He didn’t, He would not be respecting Himself. But, when the Bible says God is no respecter of persons, it means that He does not show partiality in meeting out His justice. As Deuteronomy 10 puts it, He “shows no partiality nor takes a bribe” (v. 17). In other words, God is completely fair and even-handed in His dealings.
However, there is a sense in which it can be said that God does not respect some persons because of their evil deeds. God “did not respect Cain and his offering” (Gen. 4:5) because it was not offered in faith (Heb. 11:4). Thus, the Bible also speaks of God hating Esau (Mal. 1:3) and the Nicolaitans (Rev. 2:6), not because of their person, but because of their practice. As John told the believers at Ephesus, they should “hate the deeds of the Nicolaitans” (Rev. 2:6). God loves the sinner, but hates the sin.