Question: Performing salat is an act of worship. That is, it causes one to earn rewards [thawab]. Is it wrong if I do not perform salat every day but perform them when I am available or when I retire? Similarly, is there anything wrong with not fasting in the month of Ramadan but making all of the omitted fasts up when I retire? Why is it a sin to delay earning rewards or not to earn any rewards? After all, it is I who will be held to account for all these things in the hereafter.
ANSWER
Most of those people who abandon salat mistakenly think that salat is not obligatory, but only a meritorious, good deed. But in fact abandoning salat is one of the major sins, which is more sinful than even drinking alcohol. According to the three madhahib, a person who abandons salat intentionally is put to death as a punishment. This punishment testifies to the importance of salat.

If one had a chance to make up all one's omitted salats and fasts after one has retired, one would still be considered to be committing sins as he delayed them. Besides, offering an act of worship within its prescribed time and making it up after its prescribed time are poles apart in reward [thawab]. A hadith-i sharif says:
(If a person does not fast for a single day in Ramadan, he cannot earn the thawab of this single day, even if he fasts all the year round instead of it.) [Tirmidhi]

Salat, like Ramadan fast, is an act worship performed at specific times, so it must be offered at prescribed times. To abandon a single salat is greatly sinful. The sin of it is not forgiven even if one makes it up later. One must make repentance for it as well.

He who makes up all his missed salats and fasts when he retires will only escape punishment, but he cannot earn the great rewards given in return for salats and fasts. Similarly, a person who does not sacrifice an animal on Eid al-Adha will only escape punishment if he gives its value to a poor person later on. But he cannot earn rewards for it.

It is a grave sin to omit a fard salat, and it is also a grave sin to postpone making up this omitted salat. This grave sin becomes twice itself in wickedness at each length of time wherein one could perform the omitted salat. Making repentance becomes fard upon one when one postpones making it up.

It is not right to say, "After all, it is I who will be held to account for all these things." A person who does not perform salat or who does not believe or who drinks alcohol or who does not fast in Ramadan or who commits the other sins may say the same thing. Whoever does such things does to his/her own detriment. It is necessary to do what Allahu ta'ala commanded within its prescribed time and to always refrain from what He prohibited.

Question: According to a mistaken belief among the common people, to begin performing the five daily salats regularly and then to abandon them for several years and to resume them and then to abandon them again for several years is a more grievous sin than not to begin them at all, and it is a sin to resume them after abandoning them. Is it better not to perform salat at all if it is probable that the person concerned will stop performing them later on?
ANSWER
No, it is worse than it. It is even worse than not making repentance for fear of committing a sin again. His case is like the case of a person who does not wash a plate simply because it will be dirtied again sooner or later.

It is common fallacy that resuming five daily salats after abandoning them for years is a sin. In actual fact, it is fard and brings rewards to resume them when one leaves them off for a period of time. What is sinful is not to resume salats, but to abandon them intentionally. Not performing salats adversely affect one's other deeds, too. A hadith-i sharif says:
(Whoever abandons salat intentionally [without a legitimate excuse], Allahu ta'ala does not accept his other deeds. He will be away from the protection of Allah until he repents of it.) [Isfahani]

Hadrat Imam-i Rabbani says:
One will be questioned about salat first on the Day of Resurrection. If it is found good, the questioning about one's other deeds will be easier by the help of Allahu ta'ala. (Vol. 2, Letter 67)