Tzadikim ZY”A interpreted this Possuk as follows. Tzedek, when you do righteous deeds, it shall be done with Tzedek... righteousness. Also, the ends don’t justify the means...
Justice, only justice shall you pursue, that you may live, and inherit the land which Hashem your G-D gives you. {16:20}
This means that one must pursue justice with justice. The means by which you seek to attain justice must be righteous also. Do not allow yourself to be guided by the G-Dless principle that “the end justifies the means”.
Reb Yaakov Yitzchok of Pshischoh
The Kotzker Rebbe ZY”A takes a different approach and says that sometimes the Yetzer Horoh tricks us by deluding us into being too overzealous in our righteousness. The Torah warns us to take measured step and use our head. When we start chasing Tzedek Tzedek, an extreme excess, we need to run away as it is merely the ploy of our foe the Yetzer Hara dressed in a cloak of righteousness.
