It seems we missed a long conversation regarding the old testament christians.
The topic is important to prove how could Abraham be a model of christian, Abel has a lot to teach us as well.
They lived a life that would become the gospels.
Discussion
Not to mention the typology for Christ in the OT, such as Isaac, Joseph, Jacob, etc.
"That would become" is the pertinent phrase. It is true that the One True Religion has gone by many names over the millennia, but I think it is still useful to make a distinction in degree between the pre-Christian age and Anno Domini. For one, God was present with the Israelites and spoke with the Patriarchs, but The Word Made Flesh is with us today.