Who visited Abraham in genesis 18 and what did he say?

In Genesis 18, three visitors came to Abraham, who are often interpreted as angels or a manifestation of God. One of them, identified as the Lord, told Abraham that Sarah would bear a son within a year, despite her old age. This announcement was met with disbelief from Sarah, leading to a discussion about the power of God and the promise of a child. The visit also included a forewarning about the impending judgment on Sodom and Gomorrah.