Negative commandment · Lo Ta’aseh #105 of 613
Not to place frankincense on such a sacrifice
שלא ייתן עליו לבונה
The verse · Bamidbar 5:15
וְהֵבִיא הָאִישׁ אֶת־אִשְׁתּוֹ אֶל־הַכֹּהֵן וְהֵבִיא אֶת־קׇרְבָּנָהּ עָלֶיהָ עֲשִׂירִת הָאֵיפָה קֶמַח שְׂעֹרִים לֹא־יִצֹק עָלָיו שֶׁמֶן וְלֹא־יִתֵּן עָלָיו לְבֹנָה כִּי־מִנְחַת קְנָאֹת הוּא מִנְחַת זִכָּרוֹן מַזְכֶּרֶת עָוֺן
“then shall the man bring his wife to the priest, and he shall bring her offering for her, the tenth part of an efa of barley meal; he shall pour no oil upon it, nor put frankincense on it; for it is an offering of jealousy, an offering of memorial, bringing iniquity to remembrance.”
The Rambam’s words
Not to place frankincense on such a sacrifice, as [Numbers, ibid.] continues: "...and do not place frankincense upon it."
שלא ייתן עליו לבונה, שנאמר "ולא ייתן עליו לבונה" (במדבר ה,טו).
Why · Sefer HaChinuch #367
Not to place frankincense on the sotah sacrifice
“From the roots of the commandment is that which we have written about oil, as frankincense is a beautification of the sacrifice and a pleasant smell.”
Where in the Mishneh Torah
Hilchot Woman Suspected of Infidelity הלכות סוטה