Mathematical Micro/Macro Economics Textbook Recommendation I was formerly an economics major and now also majoring in mathematics.
I want a textbook that is rigorously based on mathematics; not just using mathematics whenever the author wants, but in a more unified way to explain a concept.
I've learned enough mathematics in undergraduate level so mathematics will hardly be a problem. 
I've searched for information, but I really wanted textbooks that satisfy this specific condition; explaining concepts with sound mathematics in a unified way.

Any help is welcome.
You should also try Advanced Microeconomic Theory (3rd Edition) by (Jehle, Reny, 2011).
Note that, imho, Mas-colell-Whinston-Green (1995!) is the best choice for those with initial background in Math switching to Economics. When it comes to Economics majors the former seems to be more appropriate (and more modern).
For modern Macro with strong math see Introduction to Modern Economic Growth (Acemoglu, 2009).
To integrate the micro/macro problems with econometrics and math see Economic Modeling and Inference (Christensen &amp; Kiefer, 2009). Hope, that helps.