Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said regarding recitation behind the imam: "Remain silent for the recitation as you have been commanded, for in the prayer there is enough to occupy you (in listening silently), and the imam will suffice you (in the recitation)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10397