The phrase "reserve judgment" means to hold back or delay forming an opinion or making a decision about something until more information or evidence is available. Full definition
If I told you I had a dragon living in my garage, would you not reserve judgement until you had seen this supposed dragon? (religion.blogs.cnn.com)
We'd still reserve our judgement on their performance once we get a chance to do a full - blown comparison of the two models in our road tests. (cardekho.com)
The reviews are what I expected but I always reserve judgement till i play it myself. (novacrystallis.com)