After relieving oneself, it is obligatory to remove whatever najaasah (impurity) there is in that place, whether it is removed with water or something else, such as stones or paper or tissues, but using water is best.
The scholars of the Standing Committee for Issuing Fatwas were asked: In Britain we use tissues and paper to clean ourselves in the bathroom; is it obligatory to use water after using tissues, or not?
Praise be to Allaah alone, and blessings and peace be upon His Messenger and his family and companions.
It is permissible to use tissues and papers and the like to clean oneself, and that is sufficient if it is done properly and the place is cleaned, from front or back. But it is better if what is used for cleaning is odd-numbered, and it should not be less than three wipes. It is not essential to use water after that, but it is Sunnah. May Allaah send blessings and peace upon our Prophet Muhammad. End quote.
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan, Shaykh ‘Abd-Allaah ibn Qa’ood.
Fataawa al-Lajnah al-Daa’imah (5/125).
Shaykh Muhammad al-Saalih al-‘Uthaymeen (may Allaah have mercy on him) was asked: It is acceptable to use tissues to clean oneself after defecating?
Yes, it is sufficient to use tissues to clean oneself after defecating, and there is nothing wrong with it, because the purpose of cleaning oneself is to remove the impurity, whether it is done with tissues, cloth, dust or stones. But it is not permissible for a person to clean himself with things that are forbidden in sharee’ah, such as bones and dung, because bones are the food of the jinn, if they are from animals that were slaughtered properly; if they are from animals that were not slaughtered properly, then they are naajis (impure), and that which is impure cannot purify. As for dung, if it is naajis then it cannot purify, and if it is taahir (pure), then it is food for the animals of the jinn, because when the jinn came to the Prophet (peace and blessings of Allaah be upon him) and believed in him, he gave them some food which will not stop until the Day of Resurrection. He said to them: “For you is every bone on which the name of Allaah is mentioned, and you will find it with plenty of meat on it.” This is one of the matters of the unseen that we cannot see, but we are obliged to believe in it. Similarly, dung is food for their animals. End quote.
Majmoo’ Fataawa Ibn ‘Uthaymeen (4/112).
And Allaah knows best.