Throughout the world, all people, without exception, talk about or at least think about one issue at one point in their lives: living a long life, and to avoid dying if at all possible... Scientists have been devoting serious effort to this end for many centuries, and have tried to find formulas to make people live a longer life. However, to this day, no progress has been made. Hence, with the verse, "We did not give any human being before you immortality. And if you die, will they then be immortal? Every self will taste death. We test you with both good and evil as a trial. And you will be returned to Us," (Surat al-Anbiya’: 34-35) Allah instructs us that each person was created mortal, a fact which each will certainly face at his appointed time.
Regardless of the fact that people refrain from thinking or accepting the reality of death, the truth is that mankind is mortal. In any case, this worldly life is exceedingly short and transient. Each one is sent to this world in order to be tested for a period of time ranging from sixty to seventy years. Therefore, it would be a great mistake for anyone to base his plans on this worldly life alone, to accept this short-lived sojourn as his true life, and to forget the hereafter where he will live forever.
This fact stands out clear and simple so that all can easily comprehend it. Yet, as indicated in the following verse: "He Who created death and life to test which of you is best in action. He is the Almighty, the Ever-Forgiving," (Surat al-Mulk: 2) Allah adorned this world in order to create this environment in which man will be tested. One should not be deceived by the fact that some people compete with each other to maximize their enjoyment of these worldly blessings. Because, as the verses of the Qur’an indicate, those who live in negligence could in no way be deemed a group one should measure up to. Those, who strive to accumulate and heap up belongings, sacrifice their beliefs in order to acquire authority, and who play roles to earn the appreciation or approbation of others, are in fact running after illusory ideals. To suppose that this worldly life is real, and to run hopelessly after mundane benefits and rewards, is just as illogical, comical and humiliating as mistaking the scenes of a play for reality.
However, it should always be kept in mind that, not only those who devote themselves to this worldly life, but also those who expend effort to acquire benefits both in this world and the hereafter, are deluded. The life of this world was created as a blessing for mankind. While they are here, people should make the best possible use of its many splendors, and enjoy its many blessings. Yet, one should never idealize nor run after these blessings with excessive desire or ambition. He should utilize them all to live according to the religion in the best possible manner, to appreciate Allah, and to give thanks, after having recognized that which has been bestowed upon him by Allah. Acting in accordance with such reasoning as, "I can lead a life both to gain Allah’s consent and to make the best use of the benefits of the worldly life," would be a thought-pattern damaging to one’s sincerity.
In the following verse, referring to some of His prophets, Allah reminds mankind that the behavior of those who keep solely the hereafter in mind are the best in merit with Him:
And remember Our servants Ibrahim, Ishaq and Ya’qub, men of true strength and inner sight. We purified their sincerity through sincere remembrance of the Abode. In Our eyes they are among the best of chosen men. (Surah Sad: 45-47)
Nevertheless, Allah bestows the greatest worldly blessings upon those who sincerely turn to Him and desire the hereafter. Thus, one who distances himself from sincerity by saying, "Let me have both this world and the next," will in the end be deprived of both. One who longs for the hereafter alone will gain the blessings both of this world and the next.
Similarly, renown Turkish scholar Bediuzzaman Said Nursi said, "The secret of this matter lies in sincerity. The transient pleasures of this world become an ultimate purpose for those who have not succeeded to attain spiritual purity. Thus, the acts done by these people for the hereafter are effected by these pleasures, and their sincerity is tainted. Because worldly objectives, pleasures could not be sought along with deeds to earn otherworldly rewards. If so, sincerity is harmed." 1 He underlined that the aim to gain both worldly and otherworldly benefits emerge from a soul defficient in its education. Such thinking diminishes sincerity, and prevents one from performing pious deeds aimed at the hereafter.
In another of his works, Said Nursi noted that only those "who assume that the world is a guest house" could hope to lead the best and happiest of lives. Hence, such a frame of mind leads one to acquire Allah’s consent and to behave sincerely.
"I observe that the most fortunate person in this worldly life is he who sees the world as a military guest-house, and submits himself and acts accordingly. Through seeing it in this way, he may rise swiftly to the rank of Allah’s pleasure, the highest rank. Such a person will not give the price of a lasting diamond for something of the value of glass that will be broken. He will pass his life uprightly and with pleasure. Yes, the matters to do with this world are like pieces of glass doomed to be broken, while the lasting matters of the Hereafter have the value of flawless diamonds. The intense curiosity, fervent love, terrible greed, and stubborn desires, and other intense emotions in man’s nature were given in order to gain the matters of the Hereafter. To direct those emotions in intense fashion towards transitory worldly matters means giving the price of eternal diamonds for pieces of glass that are to be smashed." 2
In these words, Bediuzzaman compared this worldly life to a breakable bottle, and the hereafter to a diamond. Anyone acting insincerely, by becoming carried away by this worldly life, will lose his heavenly recompense, just as a man sacrificing a diamond for a worthless glass bottle. On the other hand, one who comprehends that this world is a guest-house will not commit the same error, and will exert himself to the utmost in this world and the next. (For further reading, see “Sincerity described in the Qur’an” by Harun Yahya)
1Bediuzzaman Said Nursi, Emirdağ Lâhikası (Emirdağ Letters), Vol. 1, p.86 2 Bediuzzaman Said Nursi, The Risale-i Nur Collection, The Letters Collection, The Ninth Letter
Throughout the world, all people, without exception, talk about or at least think about one issue at one point in their lives: living a long life, and to avoid dying if at all possible... Scientists have been devoting serious effort to this end for many centuries, and have tried to find formulas to make people live a longer life. However, to this day, no progress has been made. Hence, with the verse, "We did not give any human being before you immortality. And if you die, will they then be immortal? Every self will taste death. We test you with both good and evil as a trial. And you will be returned to Us," (Surat al-Anbiya’: 34-35) Allah instructs us that each person was created mortal, a fact which each will certainly face at his appointed time. 
Similarly, renown Turkish scholar Bediuzzaman Said Nursi said, "The secret of this matter lies in sincerity. The transient pleasures of this world become an ultimate purpose for those who have not succeeded to attain spiritual purity. Thus, the acts done by these people for the hereafter are effected by these pleasures, and their sincerity is tainted. Because worldly objectives, pleasures could not be sought along with deeds to earn otherworldly rewards. If so, sincerity is harmed." 1 He underlined that the aim to gain both worldly and otherworldly benefits emerge from a soul defficient in its education. Such thinking diminishes sincerity, and prevents one from performing pious deeds aimed at the hereafter. 
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