Let is consider a case where somebody could not be at his home on the eve of the fourteenth of Nissan in order to do the Bediqath Hames (search for leaven) at the appropriate time, and nominated somebody to be his Shaliah (agent) to do the Bediqah on his behalf. If, for some reason, he managed to get home earlier than expected and found that the Shaliah was in the process of doing the Bediqah but had not yet completed it, should he let the shaliyah complete the Bediqah (search) or now that he is home, should he be the one to do the search for the leaven, the Bediqath Hames?
In addition, if he himself should do the Bediqah, we have another question: should he do it with a Berakha (blessing) or without, since the Shaliyah, when he recited the blessing, had in mind the entire Bediqah, from beginning to end?
The answer is, that he should do the Bediqah and recite the Berakha (blessing).
(See Yede Hayyim, Torah Lishmah, Orah Hayyim, Sheelah Kaf)
