The law does promise to give on condition that we fulfill it's demands

"In the law as a covenant of works there is also a promise, a gracious promise of the continuance of spiritual and temporal life and, in due time, of eternal life. This promise, which flowed solely from infinite benignity and condescension in God, was made, and was to have been fulfilled, to Adam and all his natural posterity, on condition that he as their representative perfectly obeyed the precept." - John Colquhoun, A treatise on the law and gospel, pg. 15 this is on the law in general.

On the Law and the Gospel distinction

"All Scripture should be divided into these two chief doctrines, the law and the promises. In some places it presents the law. In others it presents the promise of Christ; this it does either when it promises that the Messiah will come and promises forgiveness of sins, justification, and eternal life for his sake, or when, in the New Testament, the Christ who came promises forgiveness of sins, justification, and eternal life. By 'law' in this discussion we mean the commandments of the Decalogue, wherever they appear in the Scriptures. For the present we are saying nothing about the ceremonial and civil laws of Moses." - The Book of Concords, Apology of the Augsburg Confession, Article 4 on Justification, Pg. 108. The version I have is edited by Theodore G. Tappert.