Torah Methodology #7 - Klal shehu Tzarich l'Prat/Prat shehu Tzarich l'Klal
All of what we said in the above few methodologies about general cases and specific examples only applies if the klal or the prat in question is seemingly superfluous. If, however, for the sake of simple clarity the klal requires the prat or the prat requires the klal, then it has no effect.
An example of this can be found in Deuteronomy 15:19. There, the Torah says, "Any firstborn that is born to your cattle and sheep, the male you shall sanctify to Hashem your God..." "Firstborn" is a general and "male" is a specific, but it's a necessary specific in that it comes to exclude female firstborns.
Another necessary prat can be found in Leviticus 17:13. The Torah tells us regarding ritually-slaughtered animals that "he shall pour out the blood and cover it with earth." "Cover" is a general, while "with earth" is a specific. It's a necessary specific because it comes to exclude, for example, covering the blood by throwing a blanket over it or inverting a bowl over it. Since this is necessary to explain what it meant by "cover," it carries no additional halachic significance.