МУХИ HE ОБИДИТ coll, approvVPsubj: humanusu.fut, occas. pastfixedWO
one is very gentle, inoffensive
X мухи не обидит - X wouldn't hurt (harm) a fly.
«Ты видишь ли, я его (князя Андрея) давно знаю, и Машеньку, твою золовку, люблю. Золовки - колотовки, ну а уж эта мухи не обидит» (Толстой 5). "I have known him (Prince Andrei) a long time, you see, and I am very fond of Masha, your future sister-in-law. Sisters-in-law are troublemakers they say. But Masha wouldn't hurt a fly" (5a).