OnCollisionEnter Collision not detected?

I can't figure out what I am doing wrong. I have a sphere acting as the player and a cube with the MoneyCollect tag. What is supposed to happen is the sphere collides with the cube, 100 dollars is added to the player and the cube is destroyed. For some reason, the collision of the objects is not detected, I am able to go right through the cube without triggering the collision. Here's my code:

 function OnCollisionEnter(hit : Collision){
     if(hit.collider.tag == "MoneyCollect"){
         money += 100;
         Destroy(hit.gameObject);
     }
 }