Tax bills must originate in the house of representatives. explain why the founding fathers included this provision in the constitution.

At the time the Constitution was written and this power established the Senate was made up of members appointed by the State Governors and approved by the Legislatures. Every member of the House of Representatives was to be elected. 

If the Senate generated Revenue Bills it could be viewed by citizens as taxation without representation, Since Senators were not elected and would have tyrannical powers in levying taxes. 

The Founding Fathers were brilliant in limiting the taxing ability to only those members of Congress who were elected by a popular vote of the people.