The Lord; either,
1. God the Father, whose words and oath he last mentioned, Psalms 110:4. So this is an apostrophe of the psalmist to Christ, Thy God and Father is at thy right hand, to wit, to defend and assist thee, as that phrase is used, Psalms 16:8, Psalms 109:31, and elsewhere. See Poole on "Psalms 110:1". And he, to wit, God the Father, shall strike, & c., as it follows. Although this latter clause may belong to the Messias; and as in the former he spake to him, so in this he speaketh of him; such changes of persons being very frequent in this book. Or,
2. God the Son, or the Lord, who is at thy right hand, as was said before, Psalms 110:1, shall strike, & c. So this is an apostrophe to God the Father concerning his Son. This seems best to agree with the following verses; for it is evident that it is the same person who strikes through kings, and judgeth among the heathen, and filleth, &c. And so this whole verse, and those which follow, speak of one person, which seems most probable. Shall strike through kings shall mortally wound and destroy all those kings and potentates who are obstinate enemies to him and to his church. In the day of his wrath; in the day of battle, when he shall contend with them, and pour forth the floods of his wrath upon them.