Parashas Naso
פַּ֣ר אֶחָ֞ד בֶּן־בָּקָ֗ר אַ֧יִל אֶחָ֛ד כֶּֽבֶשׂ־אֶחָ֥ד בֶּן־שְׁנָת֖וֹ לְעֹלָֽה׃
one bull of the herd, one ram, and one lamb in its first year, for a burnt offering;
Torah Temimah points to TT (verified).
פר אחד וגו׳ — מה ת״ל פר אחד ואיל אחד? פר אחד — שלא היה בעדרו כמוהו.
English: “One young bull\ldots” — what does “one bull and one ram” teach? One bull — that there was none like it in his herd.
Custom
Chazal interpret the repeated “one” as indicating that each animal was the finest of its kind.