(Al-Qalam) 68 : 3
وَإِنَّ لَكَ لَأَجْرًا غَيْرَ مَمْنُونٍ
And indeed you have uninterrupted reward.
During the period of Messenger Muhammed, Adhikr was not codified. So Messenger had to suffer and face plenty of struggles and sufferings to convey the Message of Adhikr to the mankind. Being a reward for this, he will be getting uninterrupted reward in the Hereafter. See explanation 25: 57; 48: 2; 84: 25; and 95: 6.