The final Prophet صَلَّی اللہُ تَعَالٰی عَلَیْہِ وَاٰلِہٖ وَسَلَّمَ  said:

خَمْسُ صَلَوَاتٍ فِي الْيَوْمِ وَاللَّيْلَةِ

"There are five salah in the day and night."^[1]

This refers to these salah being obligations.

Yet, in a remarkable instance of his authority, the Prophet صَلَّی اللہُ تَعَالٰی عَلَیْہِ وَاٰلِہٖ وَسَلَّمَ accepted the request of a Companion and allowed them to leave three salah, which meant they only offered two a day. As it happened, that Companion was not yet Muslim at that time, and said he would accept Islam upon the condition he only reads two salah a day. The Prophet     صَلَّی اللہُ تَعَالٰی عَلَیْہِ وَاٰلِہٖ وَسَلَّمَ allowed this.^[2]

It should be noted that this concession was specific to that Companion; nobody else can skip a single salah without a valid excuse as determined by Islamic law.

Here is a narration regarding his authority in the expiation for breaking a fast. Before this, remember, if a sane, adult, resident Muslim intentionally breaks a Ramadan fast without a valid excuse, by engaging in sexual intercourse or eating/drinking for pleasure, they must make up for the fast on another day and offer expiation. This is done by either freeing a slave, or if not possible, consecutively fasting for 60 days, or if that too is not possible, then by feeding 60 needy people two full meals each.^[3]

This is the ruling for any Muslim that breaks their fast, but the Prophet صَلَّی اللہُ تَعَالٰی عَلَیْہِ وَاٰلِہٖ وَسَلَّمَ , through his exceptional authority, excused one of his Companions from this expiation.