Question Summary:
Is it necessary to follow one madhab or Muslims can follow all four?

Question Detail:

if somebody say that i consult four madhabs and the one  which is closest to sunnah that i choose regarding religious matter. is it necessary to follow one madhab or muslims can follow all four.

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
It is important for one to follow one mazhab and have total reliance on the Imam of the mazhab. Every Imam has exerted himself in deducing various rulings of Sharia from the sources which are most relied upon, like the Qur’an and Sunnah. Every Imam is aware of the status (hukm) of a hadith and after examining various hadith, they choose the hadith which is the closest to sunnah. When choosing the closest hadith/Sunnah every Imam interoperates the hadith in a different way.
Nonetheless, this is for Ulama to understand and one cannot simply judge himself in determining which Sunnah is the closest. Just how a patient does not question the judgment of a doctor one should not question the judgment of the Imams. Thus it is imperative for one to follow one mazhab.  
For more information you may refer your wife to the following books for an in-depth understanding on the issue of Taqleed.
1- The legal status of following a Mazhab by Mufti Muhammad Taqi Usmani
http://www.islamibayanaat.com/EnglishLiterature/LegalStatusOfFollowingAMadhab-MuftiTaqiUsmani.pdf
2- Differences of the Imams by Sheikhul Hadeeth  Moulana Zakariyya (Rahmatullahi Alayhi)
http://www.slideshare.net/IslamicBooks/differences-of-the-imams-by-shaykh-zakariyya-kandhelvi-ra 
3- The obligation of adhering to a single madhhab in all its rulings
http://darulmaarif.com/taqlid-of-single-madhhab/
 
And Allah Ta’āla Knows Best
Immad Bin Arshad
Student Darul Iftaa
California, USA
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net