Eiruvin3

1(Fol. 41a) It is taught that after the death of Rabban Gamaliel, R. Joshua came and sought to nullify the former's decrees. R. Jochanan b. Nuri then arose and said: "We see that the body always follows the head; as long as Rabban Gamaliel lived, we followed his decisions, now that he is dead, thou wanteth to repeal his words. Joshua! We will not listen to thee! The Halacha has been fixed long ago according to the opinion of Rabban Gamaliel [and so it must remain]." And there were none to contradict him. [Hence we see that the decree of Rabban Gamaliel was accepted and not that of R. Joshua.] In the generation of Rabban Gamaliel, his opinion was followed, but in the generation of R. Joshua, the opinion of R. Joshua prevailed.