Commentaire sur La Genèse 27:35

במרמה WITH SUBTLETY — with cleverness (cf. Onkelos).

ויקח ברכתך, the blessing that would have been appropriate as suitable and effective for you. The blessing which Yaakov had been given (mistakenly), concerned matters of importance in our material life on this earthy both while in our own land or in the Diaspora. The reason Yitzchok had phrased it thus was because the blessing G’d had given Avraham and which was to be given to one of Yitzchok’s children was not appropriate for Esau. [the latter blessing was given to Yaakov in 28,4 so that Yaakov indeed had secured both blessings. Ed.]

ויאמר...במרמה, by making his hands appear hairy.