Brachot 49 - What to mention in the prayer after a meal
Rav Nachman explained the composition of the after-meal prayer: Moses composed for Israel the first part, the blessing of "One Who nourishes all," at the time when manna fell for them from heaven. Joshua composed the second blessing, "For the Land of Israel" when they entered the Land. David and Solomon composed together the third blessing, "The Builder of Jerusalem." David composed the segment of "Have mercy on Israel Your people and on Jerusalem Your city," and Solomon, who built the Temple, composed the segment of "The great and holy House."
After the destruction of the Second Temple, the Sages in Yavneh composed the fourth and final part, "Who is good and Who gives good," after the siege of Bethar. The "Who is good" refers to the fact that although the bodies of the people slain at Bethar were not allowed to be buried for seven years, they did not decay, and the "Who gives good" refers to the fact that finally they were allowed to be buried.
One must mentioned the covenant of circumcision and of the Land, as well as the Kingdom of the House of David. Rav Zeira once said to Rav Chisda, "Come, master, and let us study the Talmud." However, Rav Chisda replied, "I have not learned how to properly say the after-meal prayer, and I should study the Talmud?" Rav Zeira asked, "Why is this?" and Rav Chisda explained: "I was at the table of the Exilarch, and I recited the after-meal prayer, and did not mention the three covenants, and I saw Rav Sheshet straighten his neck like a snake, as if to attack me."
And why didn't Rav Chisda mention the covenentants? - Because he followed the opinion of Rav that it is not necessary. However, in doing so he neglected all other opinions, and besides, there were different version of what Rav really said.
Art: Jacques des Rousseaux - An Old Man At Prayer