ציטירנדיקער פּירוש אויף שמות 39:6

and you shall gird sackcloth over your loins (וּפִתַּחְתָּ) Jonathan renders: “And you shall gird the sackcloth over your loins.” And his interpretation is evidenced by the fact that until now, He had not commanded him to gird himself with sackcloth, that He should tell him to remove it. Moreover, when He tells him, “And you shall remove your shoes from upon your feet,” this is a sign of mourning. (It is, therefore, likely that He commanded him to gird himself with sackcloth, also a sign of mourning.) And the meaning of וּפִתַּחְתָּ is like: (Exodus 39:6) “Engraved like the engravings of a seal (מְפֻתָּחוֹת פִּתּוּחֵי חוֹתָם),” to gird himself with sackcloth tightly on his flesh, so that it appears to be engraved in his flesh.