I would like to ask you some questions that have been in my mind for a while and I am very confused about them. Regarding Isha Prayer, I have heard that there are 4 Sunnah, 4 Fard, 2 Sunnah, 2 Nafl, 3 Witr and 2 Nafl. In other daily Prayers offering the fard is enough. However, in Isha Prayer offering just fard is not enough. For it is obligatory to offer 3 Witr. Without offering the Witr, Salah is not complete. I have also heard that Witr is part of Tahajjud and different sects decided together a long time ago to include it into Isha. This means if I don't offer Witr, still my Isha is complete with just Fard. Is this true? As for Tahajjud, I have heard that it was obligatory for the Prophet (sws) only. It is not obligatory for the Ummah. Is this also true? I only offer Fard and try my best to offer it with the deepest honesty of my heart. Should I offer the Sunnah as well? I have recently started regularly offering Salah and try to perform all 5 obligatory Prayers to the best of my ability. However, I do miss Zuhr because of my comittment to work and unavailibility of suitable enviornemt. I offer Zuhr when I get home in the evening and perform this Prayer as Qada. Is my Prayer valid?
You are right in that we are obliged to offer only the five obligatory Prayers termed fard. There is no other obligation. We can offer as many optional prayers as possible. We should try to the Prophet's example and offer the optional Prayers which he used to offer and which are termed sunnah by the jurists. But there is no obigation beyond the fard Prayers.
Witr as you said are the part of tahajjud Prayer. If we offer tahajjud Prayer then we must offer witr otherwise it is not necessary. The hanafi jurists have held it to be wajib. They have based their view on the traditions tell us that the Prophet (sws) emphasised offering the witr. However, these traditions actually refer to tahajjud and not the isha Prayer. We can offer tahajjud before going to sleep as the Prophet (sws) allowed those who told him that they could not offer that in its proper time.
We are obliged to offer all the Prayers in the prescribed times. If in some extraordinary circumstances we miss a Prayer we should offer it as soon as we get out of the touble. It is not good for us to develop the habit of delaying an obligation and continue doing so for ever.