Midrasch zu Esra 2:1

Noah handed on the tradition to Shem, and he was initiated in the principle of intercalation; he intercalated the years and he was called a priest, as it is said, "And Melchizedek king of Salem… was a priest of God Most High" (Gen. 14:18). Was Shem the son of Noah a priest? But because he was the first-born, and because he ministered to his God by day and by night, therefore was he called a priest. Shem delivered the tradition to Abraham; he was initiated in the principle of intercalation and he intercalated the year, and he (also) was called priest, as it is said, "The Lord hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek" (Ps. 110:4). Whence do we know that Shem delivered the tradition to Abraham? Because it is said, "After the order of Melchizedek" (ibid.). Abraham delivered the tradition to Isaac, and he was initiated in the principle of intercalation, and he intercalated the year after the death of our father Abraham, as it is said, "And it came to pass after the death of Abraham, that God blessed Isaac his son" (Gen. 25:11), because he had been initiated in the principle of intercalation and had intercalated the year (therefore) He blessed him with the blessing of eternity. Isaac gave to Jacob all the blessings and delivered to him the principle of intercalation. When Jacob went out of the (Holy) Land, he attempted to intercalate the year outside the (Holy) Land. The Holy One, blessed be He, said to him: Jacob! Thou hast no authority to intercalate the year outside the land (of Israel); behold, Isaac thy father is in the (Holy) Land, he will intercalate the year, as it is said, "And God appeared unto Jacob again, || when he came from Paddan-Aram, and blessed him" (Gen. 35:9). Why "again"? Because the first time He was revealed to him, He prevented him from intercalating the year outside the (Holy) Land; but when he came to the (Holy) Land the Holy One, blessed be He, said to him: Jacob ! Arise, intercalate the year, as it is said, "And God appeared unto Jacob again,… and blessed him" (ibid.), because he was initiated in the principle of the intercalation, and He blessed him (with) the blessing of the world. Thus were the Israelites wont to intercalate the year in the (Holy) Land. When they were exiled to Babylon || they intercalated the year through those who were left in the (Holy) Land. When they were all exiled and there were not any (Jews) left in the (Holy) Land, they intercalated the year in Babylon. (When) Ezra and all the community with him went (to Palestine), Ezekiel wished to intercalate the year in Babylon; (then) the Holy One, blessed be He, said to him: Ezekiel ! Thou hast no authority to intercalate the year outside the Land; behold, Israel thy brethren, they will intercalate the year, as it is said, "Son of man, when the house of Israel dwell in their own land" (Ezek. 36:17). Hence (the Sages) have said, Even when the righteous and the wise are outside the Land, and the keeper of sheep and herds are in the Land, they do not intercalate the year except through the keeper of sheep and herds in the Land. Even when prophets are outside the Land and the ignorant are in the Land they do not intercalate the year except through the ignorant who are in the land (of Israel), as it is said, "Son of man, when the house of Israel dwell in their own land"(ibid.) it is their duty to intercalate the year.