The saying of the Alter Rebbe (Rabbi Shneur Zalman of Liadi) "'Love your fellow as yourself' is the vessel for 'Love Hashem, your G‑d.'"

פתגם רבנו הזקן אשר ואהבת לרעך כמוך היא הכלי לואהבת את ה' אלקיך

The Alter Rebbe teaches that in order to truly love Hashem, one must first cultivate love for their fellow human beings. The mitzvah of ואהבת לרעך כמוך (loving your fellow as yourself) serves as the practical vessel or means through which the deeper spiritual love for Hashem can be realized and expressed. By loving others, one refines their character and aligns their heart with Divine love, making it possible to fully connect with and love Hashem.

Shiurim in this topic
3771. The Rebbe is praising the work with the prisoners and emphasizes that Hashem seeks all hearts.