684. If the body or dress of a person is najis and he possesses only as much water as is likely to be exhausted if he does Ghusl or Wudhu, and no water would be available for making his body or dress Pak, he should make is body or dress Pak and pray Namaz with tayammum. But if he does not have anything upon which he would do tayammum, then he should use the water for Ghusl and Wudhu, and pray with najis body or dress.
685. If a person possesses such water or container which is not permitted to use, like when they are usurped (Ghasbi) he should perform tayammum instead of Ghusl and Wudhu.
686. When the time left for Namaz is so little that if a person does Ghusl or Wudhu he would be obliged to offer the entire prayers or a part of it after the prescribed time, he should perform tayammum.
687. If a person intentionally delays offering the prayers till no time is left for Ghusl or Wudhu, he commits a sin, but the prayers offered by him with tayammum will be valid, although recommended precaution is that he should give Qadha of the prayers.
688. If a person doubts whether any time will be left for prayers if he does Ghusl or Wudhu, he should perform tayammum .
689. If a person performs tayammum owing to shortage of time and after the Namaz he had an opportunity to do Wudhu but did not do so till the water he had is no longer with him, he will have to perform a new tayammum for subsequent prayers, even if the first tayammum had not become void, provided, of course, that tayammum continues to be his religious obligation.
690. If a person has water, but because of shortage of time he prays with tayammum and while in prayers, the water he had goes out of his possession, he will, as per recommended precaution, do tayammum again for the subsequent prayers, provided that his religious obligation continues to be tayammum.
691. If a person has only just enough time that he may perform Wudhu or Ghusl and offer prayers without its Mustahab acts like Iqamah and Qunut, he should do Ghusl or Wudhu, whichever is then necessary, and pray without those Mustahab parts. In fact, if for that purpose, he has to avoid the next Sura after al-Hamd, he should do so after doing Wudhu or Ghusl.