Comentario citado sobre I Reyes 8:61

and worship Him with a whole heart Heb. בְּלֵב שָׁלֵם. It is not stated בְּלֵבָב שָׁלֵם, which would mean two hearts, but בְּלֵב שָׁלֵם, that you shall have but one heart for our Father Who is in heaven. And so did the liturgical poet set down (in the Kedushah of Musaph of the first day of Rosh Hashanah): “You have two hearts like one for the One.” Similar to this, [we find in] (I Kings 8:61): “Let your heart [therefore] be whole (שָׁלֵם) with the Lord our God.” It is not written שְׁלֵמִים but שָׁלֵם: your two hearts will be one whole heart. And so it is explained (Gen. 18:5): “... and refresh your heart (לִבְּכֶם), afterwards you may pass on.” This teaches us that the angels have only one heart, and also in the future it will be so, as it is written: (Ps. 48:14): “Give heed (לִבְּכֶם lit., your heart) to its walls.”

And to Solomon, my son, give a perfect heart to prepare his heart to be perfect with his God, to keep His commandments, etc., and so did Solomon request (I Kings 8:57-61): “May the Lord our God be with us... Let your heart, [therefore] be perfect.”