What is the evidence for limiting the Rightly Guided Caliphs to Abu Bakr, 'Umar, 'Uthman, and 'Ali, may Allah be pleased with them?

The Rightly Guided Caliphs are Abu Bakr, Umar, Uthman, and Ali, and this is what the Ummah has agreed upon. Prophetic narrations have indicated that the Caliphate after the Prophet, peace and blessings be upon him, would last thirty years, and this includes the caliphate of these four, as mentioned in the hadith of Safinah, which detailed the duration of each of their caliphates, and found that it amounted to thirty years. The mentioned caliphate is the one that reached the highest levels of perfection.