Where is the ayah or verse in the Quran that establishes the waajeb or compulsory acts of wudu or ablution?

Answer 1

It is in Quran, verse 6, Surat Al-Maaida (chapter 5). Quran says:

أَيُّهَا الَّذِينَ آمَنُوا إِذَا قُمْتُمْ إِلَى الصَّلَاةِ فَاغْسِلُوا وُجُوهَكُمْ وَأَيْدِيَكُمْ إِلَى الْمَرَافِقِ وَامْسَحُوا بِرُءُوسِكُمْ وَأَرْجُلَكُمْ إِلَى الْكَعْبَيْنِ ۚ وَإِن كُنتُمْ جُنُبًا فَاطَّهَّرُوا ۚ وَإِن كُنتُم مَّرْضَىٰ أَوْ عَلَىٰ سَفَرٍ أَوْ جَاءَ أَحَدٌ مِّنكُم مِّنَ الْغَائِطِ أَوْ لَامَسْتُمُ النِّسَاءَ فَلَمْ تَجِدُوا مَاءً فَتَيَمَّمُوا صَعِيدًا طَيِّبًا فَامْسَحُوا بِوُجُوهِكُمْ وَأَيْدِيكُم مِّنْهُ ۚ مَا يُرِيدُ اللَّـهُ لِيَجْعَلَ عَلَيْكُم مِّنْ حَرَجٍ وَلَـٰكِن يُرِيدُ لِيُطَهِّرَكُمْ وَلِيُتِمَّ نِعْمَتَهُ عَلَيْكُمْ لَعَلَّكُمْ تَشْكُرُونَ ﴿٦﴾

Meaning English translation:

{Believers, when you are about to pray, wash your face and your hands along with the elbows and wipe your head and your feet to the ankles. If you experience a seminal discharge, manage to take (the required) bath. If you are sick, or on a journey, or have just defecated, or have had intercourse with women and cannot find any water, perform a tayammum by: touching clean natural earth with both palms and wiping (the upper part) of your face and (the back of) your hands. God does not want you to suffer hardship. He wants you to be purified. He wants to complete His favors to you so that perhaps you would give Him thanks. (6)} [Quran, chapter 5, verse 6]