Why did he say "Lo l'Adam Tishpetu Ki la'Shem"?
'Rashi': Do not say, it is not so bad if we tilt the verdict, to vindicate our friends, tilt the judgment of Aniyim and favor the rich - therefore, it says la'Shem. If you obligated the innocent, it is as if you took from your Creator and made Din Shamayim crooked. Refer to 19:6:2:1.
Malbim: Refer to 19:6:2:5.
What do we learn from "v'Imachem bi'Dvar Mishpat"?
'Rashi': Consider every judgment as if Hashem stands in front of you.
'Rashi' citing Sanhedrin 6b: Perhaps a judge will say 'why should I judge?' (Perhaps I will err and be punished! "V'Imachem bi'Dvar Mishpat" - a judge judges according to what he sees. (If he does so, he will not be punished.)
Radak #1: Fear Him as if He is with you in judgment.
Radak #2: He will help you in judgment if you will fear Him.
Malbim: "Elokim Nitzav b'Adas Kel" are the litigants; "b'Kerev Elokim Yishpot" are the judges - He is among the judges and judges with them. "V'Imachem bi'Dvar Mishpat" - it is as if He is a litigant - injustice done to a litigant is as if it is done to Him.
