Overall meaning :
Allah commands His believing servants to respond to Him and the Messenger, by showing obedience to them, when the Messenger calls them to whatever is bound to set their affairs aright and gives life in the full sense of the word to their bodies and spirits both in this world and the hereafter. They should know, He warns them, that He comes in between a person and his heart if He so wills, so much so that one cannot possibly perceive truth or falsehood with it anymore unless He wills, and that to Him will they all be returned and gathered on the Day of Judgement and be repaid according to their deeds.
He also directs them to beware of an affliction from their Lord which will not smite exclusively those who do wrong by disobeying Him but will rather smite both the wrongdoers and others who see evil being committed but do not forbid it while they are able to, and He urges them to know that He is severe in exacting retribution.
He further directs them to remember the time when they were few in number and persecuted by their enemies, ever fearful that their enemies would snatch them away and seize them swiftly, one after the other, but He sheltered them, strengthened them and continued supporting them until they prevailed over their enemies, and provided them with good things so that they might give thanks.