מדרש על מנחות 121:18

(Bamidbar 6:20) "And the Cohein shall lift them, a lifting before the L-rd": back and forth and up and down, as it is written (Shemot 29:27) "which was waved and which was lifted." Lifting is being compared to waving. Just as waving is back and forth, so, lifting; and just as lifting is up and down, so, waving — whence they ruled: the mitzvah of waving — back and forth, up and down. (Ibid.) "before the L-rd": in the east. For wherever "before the L-rd" is written, in the east is understood unless it is specified otherwise. "It is holy to the Cohein, in addition to the breast of waving and the thigh of lifting": Why is this stated? (i.e., it is already written [Vayikra 7:34]) "For the breast of waving, etc.") For in "For the breast of waving and the thigh of the lifting have I taken from the children of Israel from their peace-offerings," the peace-offerings of the Nazirite are also subsumed, and Scripture (here) removed them from their context for the ram's shoulder requirement. This tells me only of the latter. Whence do I derive (the same for) the breast and the thigh? It follows a fortiori, viz.: If individual peace-offerings, which do not require the giving (to the Cohein) of the shoulder, do require the (giving of) breast and thigh, then the Nazirite peace-offerings, which do require the giving of the shoulder, how much more so do they require the giving of breast and thigh! Now if I can derive this a fortiori, why need it be written (Ibid.) "It (the shoulder) is holy to the Cohein, in addition to the breast of waving and the thigh of lifting"? We are hereby apprised that every thing (in this instance, Nazirite peace-offerings) which was included in a general formulation and departed from that formulation for the sake of a new learning (in this instance, the giving of the shoulder) may not be returned to its general formulation until Scripture explicitly does so.