To the best of my understanding, and with the help of the wise counsel here at BH (regarding grammar and additional textual information, although each contributor has independently arrived at a different interpretation) I am answering this question as follows:
The Lord our Righteousness is speaking through this NT passage and also through the quoted OT passage. In addition (unfortunately, due to the translators' systemic theology) He is referred to as "it".
Thus, I submit for everyone's further consideration and remembrance the following:
...and this is his name whereby he shall be called, THE LORD OUR RIGHTEOUSNESS. (Jer 23:6b)
Jesus Christ is the only "righteousness which is of faith". And, He speaketh still.
6But the righteousness which is of faith (the Lord our Righteousness) speaketh on this wise
8But what saith it (He)?
[Italics mine]