Ibadah means, ‘obedience and compliance of the creation to the Orders and Commands of the Creator.’ When Allah Commands us to pray five times a day, then Salaat here is Ibadah and obedience to Allah. Similarly, obedience to everything that He has commanded is worship and refusal to perform any of it is disobedience and road to Kufr (disbelief). So, we are obliged to carry out His Command and not ask questions as to why do we pray five times and why four rak’ahs or three rak’ahs? We obey His Orders even if we do not understand the wisdoms behind it because the reason behind the worship is that it is a Command of our Lord – Allah, the Exalted.
Mu’aathah said, ‘I asked Aishah, why must we make up the fasts missed due to our menstruation, and not the prayers?’ She said, ‘That was what the Messenger of Allah told us to do. We were ordered to make up the fasts and were ordered not to make up the prayers.’ [Fiqhus-Sunnah, (1.71A)]
Iblees rejected the Command of Allah and questioned His Wisdom when he said, ‘I am better than him [Adam], You created me from fire, and him You created from clay.’ [Soorah al-A’raf (7): 12]
This act is disobedience to Allah and Kufr (disbelief), and Allah tells us in the Qur’aan, ‘And (remember) when We said to the angels, ‘Prostrate yourselves before Adam.’ And they prostrated except Iblees, he refused and was proud and was one of the disbelievers (Kuffar).’ [Soorah al-Baqarah (2): 34]