Narrated Amr bin Amir:

Anas said, "The Prophet peace be upon him used to perform ablution for every prayer." I asked Anas, "What did you used to do?' Anas replied, "We used to pray with the same ablution until we break it with Hadath."

The expression "for every prayer" in the hadith means "for every fard prayer". Some Shiites and apparent groups based on this hadith and say, "It is wajib for every prayer to make an ablution". However, in the second part of this hadith, if the Companions did not break the wudu, they were satisfied with the previous ablution. Other hadiths also indicate that it is permissible to perform more than one prayer with one ablution. That is why the Islamic scholars did not accept the saying, "It is obligatory to make new wudu on every prayer". New ablution for every prayer is a virtue, a light upon the light, and an additional goodness. But it is not wajib.

Sulaiman ibn Buraida reported: 

The Messenger of Allah peace be upon him performed five prayers with the same ablution in the occasion of the Conquest, and he wiped over his socks. Umar said to him (the Prophet): I saw you doing a thing today that you never did. He said: I did it deliberately.

This means that those who make a new ablution for every prayer and those who perform several salats with the same ablution are right.