What are the ramifications of the statement "ve'Chol Erk'cha Yih'yeh be'Shekel ha'Kodesh"?
Rashi: It means that wherever the Torah mentions 'Shekalim' in the current Parshiyos, it means a Shekel ha'Kodesh - a Sela, which is equivalent to two regular Shekalim.
Erchin, 7b: It means that the minimum assessment in the current Parshiyos is one Shekel ha'Kodesh 1 (which is equivalent to a Sela).
Sifra: It implies that Kodshim can only be redeemed with money. However, the Pasuk in Korach Bamidbar "u'Feduyav mi'Ben Chodesh Tifdeh" - in connection with Pidyon ha'Ben - implies that one may redeem Kodshim with anything. We therefore include Metalt'lin and preclude Karka'os, Avadim and Sh'taros. 2
Torah Temimah: If for example, a poor man cannot afford to pay Hekdash the Erech of the person whose Erech he declared, then the minimum that the Kohen assesses him for is a Shekel ha'Kodesh (See Torah Temimah).
Refer to Bamidbar, 18:16:3:1
How much is twenty Geirah?
Rashi: Twenty Geirah is synonymous with twenty Ma'ah. 1
Which is a better-known name for the same coin. Rashi (citing Bechoros, 50a): The Chachamim added a sixth to its value and stated that six silver Ma'os equals one Dinar - in which case a Sela equals twenty-four Ma'os.
Why does the Torah insert the (otherwise superfluous) word "Esrim Geirah Yih'yeh ha'Shakel"?
Bechoros, 3a: To teach us that Beis-Din are permitted to add to the value of a Shekel. 1
Bechoros, Ibid.: Whereas "Esrim Geirah Hu" - in Korach Bamidbar, 18:16, implies that they are not permitted to detract from it.
