As if it Were Already Done

Sefer Ohev Yisroel explains this verse as follows: ‘And it will be if you listen to these laws and guard them and Hashem, your G-d, will protect the covenant…’ Hashem is telling us that if we listen and commit to do the mitzvos, then He will uphold His covenant with us, even if we do not deserve it. Although we have yet to properly fulfill the mitzvos, He considers it as if we have already done them, and He rewards us accordingly.