39. This paragraph is a parenthesis, which has been inserted at the end of one theme and before the commencement of the other. It is obvious from this that this Surah was sent down after a long delay. At that time the Prophet (peace be upon him) and his companions were passing through very hard times and were always expecting a revelation to guide and comfort them. When Angel Gabriel came with other angels with this revelation, he at first delivered that part of the message which was immediately needed. Then before proceeding further, he said these words by the leave of Allah as an explanation for the delay and to give them comfort from Allah and counsel of fortitude. This interpretation is not only borne out by the wording of the passage but also by some traditions of the Prophet (peace be upon him), which have been cited by Ibn Jarir, Ibn Kathir, and the author of Ruh-ul-Maani in their commentary on this passage.
40. That is, you should not only follow strictly the way of service and face all the obstacles and afflictions with patience, but also should not get uneasy, if there is a delay in revelation and help. You should rest content with His service as an obedient servant and perform persistently the duties and responsibilities entrusted to you as a servant and Messenger.
41. The word Samiya literally means a name sake. Here it implies: Allah is the only Deity. Do you know of any other deity besides Him? If there is none, and you know that there is none, then you do not have any alternative but to serve Him and obey His commands.