He prohibited us from delaying vows, voluntary offerings and other sacrifices which are obligatory for one. And that is His, may He be exalted, saying, "When you make a vow to the Lord [...], do not delay, etc." (Deuteronomy 23:22). And the tradition appeared (Rosh Hashanah 4b), that one has not transgressed this negative commandment until three consecutive holidays have passed him by. And the regulations of this commandment have already been explained in the first chapter of Rosh Hashanah. (See Parashat Ki Tetzei; Mishneh Torah, Sacrificial Procedure 14.)