When the time approached in which, according to the promise made to Abraham, his children would be redeemed, it was seen that they had no pious deeds to their credit for the sake of which they deserved release from bondage. God therefore gave them two commandments, one bidding them to sacrifice the paschal lamb and one to circumcise their sons.[201] Along with the first they received the calendar in use among the Jews, for the Passover feast is to be celebrated on the fifteenth day of the month of Nisan, and with this month the year is to begin. But the computations for the calendar are so involved that Moses could not understand them until God showed him the movements of the moon plainly. There were three other things equally difficult, which Moses could comprehend only after God made him to see them plainly. They were the compounding of the holy anointing oil, the construction of the candlestick in the Tabernacle, and the animals the flesh of which is permitted or prohibited.[202] Also the determination of the new moon was the subject of special Divine teaching. That Moses might know the exact procedure, God appeared to him in a garment with fringes upon its corners, bade Moses stand at His right hand and Aaron at His left, and then, citing Michael and Gabriel as witnesses, He addressed searching questions to the angels as to how the new moon had seemed to them. Then the Lord addressed Moses and Aaron, saying, "Thus shall My children proclaim the new moon, on the testimony of two witnesses and through the president of the court.[203] When Moses appeared before the children of Israel and delivered the Divine message to them, telling them that their redemption would come about in this month of Nisan, they said: "How is it possible that we should be redeemed? Is not the whole of Egypt full of our idols? And we have no pious deeds to show making us worthy of redemption." Moses made reply, and said: "As God desires your redemption, He pays no heed to your idols; He passes them by. Nor does He look upon your evil deeds, but only upon the good deeds of the pious among you."[204] God would not, indeed, have delivered Israel if they had not abandoned their idol worship. Unto this purpose He commanded them to sacrifice the paschal lamb. Thus they were to show that they had given up the idolatry of the Egyptians, consisting in the worship of the ram.[205] The early law was different from the practice of later times, for they were bidden to select their sacrificial animal four days before the day appointed for the offering, and to designate it publicly as such, to show that they did not stand in awe of the Egyptians.