516 letters, 59% in the 1950s. Love of a fellow Jew is the gate — the Alter Rebbe's sha'ar ha'aliya; the three loves (of G-d, Torah, and Israel) are one. It reaches the Jew at the end of the earth you've never seen, and kol Yisroel arevim is read three ways (sweetness, intermixture, responsibility). The one qualification on the unconditional love: draw him up toward you, never lower yourself to him — the oil spreads and draws close, but doesn't mix, and rises above.
He treats ahavas Yisroel not as a fine trait but as the gate — דא תרעא לאעלאה, the door through which everything else in avodah must pass. Love of G-d, love of Torah and love of a fellow Jew are, in the Alter Rebbe's reading, one and the same. The scope is unconditional: even the Jew at the ends of the earth, even the simplest — "because he is a Jew."
The recurring claims about loving a fellow Jew, by how often each surfaces.
One phrase he turns over three ways: כל ישראל ערבים זה בזה — arevim as sweetness, as intermixture, and as responsibility. Out of ahavas Yisroel all Jews are blended into one and each is answerable for the other.
The rule is total: love reaches the farthest, simplest Jew, without condition. What he qualifies is not whom but how. Drawing a distant Jew close must raise him toward you, never lower you to him — and the love is fixed on the eternal soul, never on the failing, which is bounded and can be erased. Here, verbatim.