Pledge yourself with prayer and remain steady on it; offer prayer as much as possible and seek nearness (of Allah) through it, because it is, (imposed) upon the believers as (a) timed ordinance (Qur'an 4:103). Have you not heard the reply of the people of Hell when they were asked: 
What hath brought you into the hell? They shall say: We were not of those who offered the regular prayers (to Allah)! (Qur'an, 74:42-43). 
Certainly, prayer drops out sins like the dropping of leaves (of trees), and removes them as ropes are removed from the necks of cattle. The Messenger of Allah - the peace and blessing of Allah he upon him and his descendants - likened it to a hot bath situated at the door of a person who bathes in it five times a day. Will then any dirt remain on him?
Its obligation is recognised by those believers whom neither the adornment of property nor the coolness of the eyes produced by children can turn away from it. Allah, the Glorified, says:
Men whom neither merchandise nor any sale diverteth from the remembrance of Allah and constancy in prayer and paying the poor-rate; ... (Qur'an. 24:37)
Even after receiving assurance of Paradise, the Messenger of Allah - peace and blessing of Allah be upon him and his descendants - used to exert himself for prayers because of Allah, the Glorified's command.
And enjoin prayer on thy followers, and adhere thou steadily unto it, ... (Qur'an, 20:132).
Then the Holy Prophet used to enjoin his followers to prayer and exert himself for it.
Then, Islamic tax has been laid down along with prayer as a sacrifice (to be offered) by the people of Islam. Whoever pays it by way of purifying his spirit, it serves as a purifier for him and a protection and shield against fire (of Hell). No one therefore (who pays it) should feel attached to it afterwards, nor should feel grieved over it. Whoever pays it without the intention of purifying his heart expects through it more than its due. He is certainly ignorant of the sunnah, he is allowed no reward for it, his action goes to waste and his repentance is excessive.
Then, as regards fulfilment of trust, whoever does not pay attention to it will be disappointed. It was placed before the strong skies, vast earths and high mountains but none of them was found to be stronger. vaster, or higher than it. If anything could be unapproachable because of height, vastness, power or strength they would have been unapproachable, but they felt afraid of the evil consequences (of failure in fulfilling a trust) and noticed what a weaker being did not realise it, and this was man.
. . . Verily he was (proved) unjust, ignorant. (Qur'an, 33:72)
Surely, Allah, the Glorified, the Sublime, nothing is hidden from Him of whatever people do in their nights or days. He knows all the details, and His knowledge covers them. Your limbs are a witness, the organs of your body constitute an army (against yourself), your inner self serves Him as eyes (to watch your sins), and your loneliness is open to Him.
(1) Al-Kulayni, al-Kafi, V, kitab al-jihad, 36.