who alone could enter the holy of holies and on what occasion
Holy of Holies The Holy of Holies was covered by a veil, and no one was allowed to enter except the High Priest, and even he could only enter once a year on Yom Kippur (the day of atonement), to offer the blood of sacrifice and incense before the mercy seat. The Bible reports that in the wilderness, on the day that the tabernacle was first raised up, the cloud of the Lord covered the tabernacle (Exodus 40:33-40:34). There are other times that this was recorded, and instructions were given that the Lord would appear in the cloud upon the mercy seat (kapporet), and at that time the priests should not enter into the tabernacle (Leviticus 16:2). According to the Hebrew Bible, the Holy of Holies contained the Ark of the Covenant with representation of Cherubim. Upon completion of the dedication of the Tabernacle, the Voice of God spoke to Moses "from between the Cherubim" (Numbers 7:89).
Sailing to Byzantium Written in 1926 (when Yeats was 60 or 61), "Sailing to Byzantium" is Yeats' definitive statement about the agony of old age and the imaginative and spiritual work required to remain a vital individual even when the heart is "fastened to a dying animal" (the body). Yeats's solution is to leave the country of the young and travel to Byzantium, where the sages in the city's famous gold mosaics could become the "singing-masters" of his soul. He hopes the sages will appear in fire and take him away from his body into an existence outside time, where, like a great work of art, he could exist in "the artifice of eternity." In the final stanza of the poem, he declares that once he is out of his body he will never again appear in the form of a natural thing; rather, he will become a golden bird, sitting on a golden tree, singing of the past ("what is past"), the present (that which is "passing"), and the future (that which is "to come").