Halakhah su Levitico 20:25

If, while in the middle of one's prayer [i.e. Amidah], he feels an urge [to relieve himself], he should maintain himself [in prayer] until he has finished, and not interrupt. And if at the time of the Recitation of the Sh'ma and its blessings he feels an urge, regardless of whether it is for urinating or defecating, he may read it normally. Rem"a: And [this is] specifically if one does not feel so much of a urge that there is an element of "Do not cause an abomination" (Leviticus 20:25). But if this is not so, it is better to interrupt [one's prayer and use the toilet] (Responsum of the Rashb"a, section 131, who ruled that it is permissible, and the Terumat haDeshen section 16, who ruled that it is prohibited. And one needs to distinguish such [i.e. between those sources]) And if one wanted to distance himself and urinate [during the Recitation of the Sh'ma and its blessings], he may.

That is that He commanded us to check for the signs of [permissible] fish, which are written [in the Torah]. And that is His, may He be blessed, saying, "These are what you may eat from all that is in the water" (Leviticus 11:8). And in explanation, they said in the Gemara (Chullin 66b), "One who eats an impure fish transgresses a positive and a negative commandment." As its statement - "These are what you may eat" - [makes] me understand that one besides these may not be eaten. And a negative commandment that is derived from a positive commandment is a positive commandment. Behold it has been made clear that its statement, "These are what you may eat," is a positive commandment. And the content of our saying that this is a positive commandment is what we have mentioned to you; and that is our being commanded to administer these signs, and to say that this is permissible to eat and this is not permissible to eat - as it is stated (Leviticus 20:25), "And you shall distinguish the clean beast from the unclean." And their distinguishment is though the signs. And therefore each and every one of these four types and their signs is a separate commandment - meaning the signs of the beasts and the animals; the birds; the locusts; and the fish. And we have already explained their expressions in each of the verses as an individual commandment. And the regulations of this commandment - meaning the signs of the fish - have already been explained in Chapter 3 of Tractate Chullin. (See Parashat Shemini; Mishneh Torah, Forbidden Foods 1.)

The command of checking the signs of a beast or animal: That we were commanded to check the signs of a [domesticated] beast or [wild] animal when we want to eat of them - and they are that it brings up (chews) its cud and completely splits [its hoof], as it is stated (Leviticus 11:2-3), "This is the animal that you shall eat, from every beast upon the earth: All that separate the hoof, etc." And the language of Sifri, Shemini, Chapter 3:1 is "'It shall you eat' - it is for eating, but an impure animal is not for eating"; meaning to say, and we learn from it a negative commandment for an impure animal. And a negative commandment like this is called a negative commandment that comes from the implication of a positive commandment. And it is stated in another place, "And you shall differentiate between a pure beast and an impure, etc." (Leviticus 20:25). And it is also written (Leviticus 11:47), "To differentiate between the impure, etc."