Mu' adh ibn Jabal (Rady'Allahu Anhu) related: "I was riding behind RasulAllah (sallallahu Alaihe wa sallam) when he said to me:

'O Mu'adh! Do you know what is due to Allah from His creatures, and what is due to them?' I responded: 'Allah and His Prophet know best.' He continued: 'What is due to Allah from His creatures is to serve Him alone and never to associate any other being with Him. What is due to them is not to punish any person who does not associate aught with Him.' I said: 'O RasulAllah (sallallahu Alaihe wa sallam), may I not then give the glad tidings to the people?' He replied: 'No! Do not reassure them lest they rely on the promise and lapse in their service to Him'."

[The foregoing hadith is reported in the sahihayn Bukhari & Muslim]