Allah (God) holds everybody who has a sound mind and consciousness responsible for living by the Qur’an’s morality and for fulfilling the Qur’an’s commands. Those who perform acts of worship live a good life in this world and earn eternal life inHeaven. Intentionally deferring these prayers with such thoughts as "I’d better enjoy my youthful years, I can worship when I get older and thus earn the life in the Hereafter" may cause people to lose their lives in the Hereafter, for "There is no repentance for people who persist in doing evil until death comes to them and who then say: ‘Now I repent,’ nor for people who die as unbelievers. We have prepared for them a painful punishment" (Surat an-Nisa’, 18).
Also remember that no one knows when he or she will die. Thus, it is a great mistake to defer one’s worship as if he knows the time of his death, for after death there are no more opportunities, regardless of the level of regret or of the desire to be sent back.
It is not acceptable not to perform acts of worship, saying: "I have a pure heart"
The world is a place of testing for everyone. Allah informs humanity of this fact in the Qur’an: "He Who created death and life to test which of you is best in action..." (Surat al-Mulk, 2). As a requirement of this test, people are accountable for every action and every act of worship that they actually perform or defer. In such a case, the chastity of one’s heart alone cannot be a measure. No doubt this chastity, goodwill, and honest personality are valuable in Allah’s Sight, but the most significant sign of chastity and sincerity is the meticulous fulfillment of His commands. Therefore, no matter how benevolent they claim to be, people who do not perform the prescribed acts of worship, stand in awe of Allah, and do not act according to His good pleasure and the Qur’an will not meet with what they expect in the Hereafter. Besides these, only the Qur’an can measure the "chastity of heart." In other words, people can say that they are chaste only if they are sincere in compliance with the moral values of the Qur’an. Thus, it is senseless for them to claim to have a chaste heart based upon their own code of values.