Do Quran & Hadith provide guidance on how to deal with doubts in nikah, writing, & impurity?

Could you give me some information from Quran and hadith about doubts and how far you need to go to get rid of them, particularly in the following 3 instances. 1) If you have doubt whether the names and things were said properly in the nikah do you have to go to the madressah and get a certificate to make sure. What if there is not certificate available? 2) If you have doubt you might have written something blasphemous during some things you have written, do you need to go through everything you’ve written to check if you did. Obviously you did not want to write anything blasphemous. 3) If you have doubt that a certain place might be impure do you need to enquire of someone who would know whether this is the case.