It was two-sided...
It was two-sided, one inside the minds and the other in the political life of the nation. He was working to change both. On the first front he was working in order to condemn the rule of the Umayyad family, nullify the legitimacy of their power and expose their crimes and corruption to the Muslims.
On the second front, the Imam was trying to break away the barrier of fear from the minds of the Muslims and imbue them with enthusiasm, bring back the will-power which they had been robbed of and restore their trust, strength, courage, and reliance on God. The Imam was striving to remove the widespread defeatist tendency that was affecting the Muslims. He knew that the reason behind all this defeatism was internal: love for the world and neglect of the hereafter.
He thought that the way to treat this terrible psychological problem was to make the hereafter the object of desire not the world, and make them overcome the fear of death. It was against this background that the Imam wrote to his brother Muhammad ibn al-Hanafiyyah and addressed the community of his grandfather. He presented the diagnosis of the problem and gave the precise prescription for its treatment.
“[Know that] the world is as if it has never been and the hereafter is as if it has always been. Peace.” Devotion To God And Withdrawing From The World The statement of the Imam, precise as it was, contained the whole solution: exclusive devotion to God by reducing the charm and glamour of the world.
The Commander of the Faithful (as) once said concerning Uthman ibn Maz‘un (may God have mercy on him) “I used to have a brother in [faith and the love of] God whose contempt for the world exalted him in my eyes.” In addition to cutting down the fascinating effect of the world, one has to attach great importance to the hereafter in his mind and arouse interest in it.
This is what the Imam alluded to in his address: “[Know that] the world is as if it had never been and the hereafter is as if it has always been.” Now let us ponder over this statement of the Imam and discuss both parts of it. But before that we shall ask: what is ‘the world’ and what is ‘the hereafter’? What Are The World And The Hereafter? What is meant by the world is attachment to it and what is meant by the hereafter is having a relationship with God and wanting to meet Him.
With this, one can live in the world while being among the people of the next world, and we can describe them as living in the world and not living in it.