493. Al HaMichya
Brachos 3:13
The “one bracha that is like three” (al hamichya) includes themes from the first three brachos of bentching, as follows:
Blessed are You, Hashem our God, King of the universe, for that which gives life and for the sustenance, and for the precious, good and spacious land that You granted our ancestors as an inheritance. Have mercy, Hashem our God, on us and on Your entire people of Israel, and on Your city of Jerusalem, and on Zion, where Your glory resides. May You cause us to ascend there and to rejoice in its rebuilding, and we will bless You in holiness and purity. Blessed are You, Hashem, for the land and the sustenance.
On Shabbos and yom tov, one inserts a brief reference to the unique nature of the day, just as one does in bentching.
Brachos 4:1
Whoever bentches or recites al hamichya should do so in the place where he ate. If he ate while walking, he should sit down where he finished eating in order to say the brachos; if he ate while standing, he should sit down there in order to say the brachos. If one forgot to bentch and remembered before his food was digested, he may bentch where he remembered. If he did not bentch where he ate on purpose, he must return to where he ate in order to bentch. If he happened to bentch where he remembered, he still fulfills his obligation. Similarly, if a person bentched while standing or while walking, he still fulfills his obligation. However, one should only bentch or say al hamichya while seated in the place where he ate.