Psalm 51/Notes/Grammar.v. 14.400108
From Psalms: Layer by Layer
According to HALOT, סמך here (as in Gen 27:37) takes two objects indicating the person supported and the instrument with which the person is supported. The syntax leaves it ambiguous whether the spirit is God's supporting spirit or the psalmist's spirit by which God supports the psalmist. Some translations (e.g., JPS 1985) prefer to read תִסְמְכֵנִי as a third-person singular jussive with רוּחַ נְדִיבָה as subject, but the context of second-person imperatives and yiqtols argues rather for the second-person reading in this clause.