Midrash su Levitico 24:7

5) (Vayikra 24:7) ("And you shall place near the two pure frankincense; and it shall be a memorial for the bread, a fire-offering to the L–rd.") I might think that one row is intended. (But this is not so, for) it is written here "row," and above "two rows." Just as there, two rows are indicated, so, here.

6) "pure frankincense": it should be clear. "and it shall be for the bread": It is indispensable to the bread. "and it shall be for the bread": We are hereby taught that (piggul thoughts [thoughts effecting rejection of the offering] in respect to) the frankincense — hold back, render piggul, and invalidate the bread. "and it shall be for the bread": It is not placed on top of the bread, but into the censers with bottoms, which are placed on the table so as not to crack the bread.

7) "as a memorial": "memorial" is written here, and elsewhere (Vayikra 5:12, in respect to a meal-offering.) Just as there a fistful, here, too, a fistful — whereby we are taught two fistfuls are needed: one, for one row, and another for the other.