What are the names of the scholars from among the Salaf and the Khalaf who issued a fatwa that the three divorce pronouncements issued separately do not take effect, and what is their evidence for that?

The majority of scholars hold that a triple divorce, whether uttered in a single phrase or separately, counts as three divorces.

However, Sheikh al-Islam Ibn Taymiyyah and those who followed him—a view chosen by the two Sheikhs Ibn Uthaymeen and Al-Sa'di—are of the opinion that a triple divorce counts as only one divorce. They cite as evidence the Almighty's saying: "O Prophet, when you [Muslims] divorce women, divorce them for [the commencement of] their waiting period" (Quran 65:1), and the agreed-upon Hadith of Ibn Abbas: "During the time of the Messenger of Allah, peace and blessings be upon him, Abu Bakr, and for a period of Umar’s caliphate, a triple divorce was considered one." They believe that Umar's enforcement of the triple divorce as three was a policy to prevent people from rushing into it.