We further find that if someone loves his fellow Jews, it is a sign that he loves Hashem.
The Maharal (Nesivos Olam, Ahavas Hareya, Perek 1) writes: “Loving people is also a form of loving Hashem. One who loves someone loves all that He creates. Therefore, one who loves Hashem loves His creations. But if one hates people, it is impossible for him to love the one who created those people.”

The Maharal explains that loving one's fellow Jews is a profound expression of loving Hashem, as one who loves the Creator loves His creations.

Ahavas Hashem and Ahavas Yisroel

Collected Thoughts on the Weekly Parshah From Rabbi Meir Isamar Rosenbaum shlita