Is it sufficient in ablution (wudu') and prayer (salat) to confine oneself to the obligatory acts only, performing each once, and is the prayer thereby considered valid?

One should not proceed with ablution and prayer in this manner, nor encourage people to do so, because it involves abandoning many obligations according to some scholars, such as the Hanbalis, who consider the glorification in bowing (rukūʿ) and prostration (sujūd) obligatory, as well as the remembrance upon rising from bowing and between the two prostrations. They also consider the two salutations (taslīm) a pillar of prayer. Therefore, intentionally performing prayer in this manner is not considered valid by them. Prayer is to be established in the prescribed manner that has been commanded, for the Prophet, peace and blessings be upon him, said: "Pray as you have seen me praying." Establishing prayer with its remembrances and presence of heart is among the causes of a sound heart. Whoever misses this has missed great rewards, perfect humility, and the blessings of prayer. The same applies to ablution (wudūʾ). Rinsing the mouth and sniffing water into the nose are obligatory according to the Hanbalis, and saying "Bismillah" (in the name of Allah) is obligatory. Limiting oneself to washing the limbs only once misses the complete and recommended purity.