The intent a person has while performing a mitzva is, in this sense, equal to the act of performing the mitzva.
The superiority of a mitzva, which comes from God and not from man, is actualized through the intent a person has while performing the mitzva, as much as it does in the act of the mitzva.
The intent is not an addition to the act of the mitzva that a person contributes to God of his own volition.
Rather, it is part and parcel of the performance of the mitzva as God commanded, emanating from God’s will, no different from His will for the physical performance of the mitzva.
Rabbi Adin Steinsaltz