Rashi on Deuteronomy 22:1/רש"י על דברים כ״ב:א׳

1והתעלמת [THOU SHALT NOT SEE ANY OF THY BROTHER'S HERD … GO ASTRAY] AND HIDE THYSELF [FROM THEM] — i.e. one, as it were closes his eyes tight as though one does not see it.

2לא תראה … והתעלמת THOU SHALT NOT SEE … AND HIDE THYSELF [FROM THEM] — “thou shalt not see it, that thou hide thyself from it” (i.e. you see it only to hide thyself from it), this is the plain sense of the verse. Our Rabbis, however, said that the omission of the particle לא before the verb והתעלמת (one would expect כי תראה … לא תתעלם) suggests: There are times when you may hide yourself from it, etc. (Sifrei Devarim 225:4; Bava Metzia 30a).