and counting can only be done during the day and not at night, as it says: ''And she shall count for herself seven days'' (Leviticus 15:28), she cannot immerse herself until after sunrise, although here she has to count only one day.

§ The mishna concludes: And with regard to all these things, if one did them after daybreak they are valid. The Gemara asks: From where is this matter derived, that from daybreak it is already considered daytime? Rava said: As the verse states: ''And God called the light [or] day'' (Genesis 1:5), meaning: To that which was becoming lighter and lighter he called day. The Hebrew word or is not to be understood in its usual sense of light, but as a verbal noun: that which is becoming lighter and lighter. It teaches that as soon as light begins to appear in the sky it is called daytime.

The Gemara raises a difficulty with this interpretation: However, if it is so that Rava’s interpretation of this phrase is correct, the following phrase: ''And the darkness [ḥoshekh] He called night'' (Genesis 1:5), should be interpreted in a similar fashion: That which was becoming darker and darker He called night, so that immediately after sunset it would be considered nighttime. But don’t we maintain that until the stars come out it is not nighttime? We are forced to say that ḥoshekh literally means darkness, and similarly, or in the first part of the verse literally means light.

Rather, Rabbi Zeira said: We derive this halakha from here, as it is stated: ''So we labored in the work; and half of them held the spears from the rising of the morning till the stars appeared'' (Nehemiah 4:15), where ''rising of the morning'' means daybreak, and the next verse states: ''So that in the night they may be a guard to us; and labor in the day'' (Nehemiah 4:16). This demonstrates that the day begins with the dawn.

The Gemara clarifies Rabbi Zeira’s statement: What need is there for the additional verse introduced by the words ''and it states''? Why does the first proof-text not suffice? The Gemara explains: The second verse comes to deflect the following possible objection: You might say that even after ''the rising of the morning'' it is not yet considered day, and that from the time when the sun sets it is already considered night, and in this particular incident it happened that they began their work early, before the official beginning of daytime, and remained working late, after the official end of daytime. Therefore, Rabbi Zeira continued and said: Come and hear that which is stated in the next verse: ''So that in the night they may be a guard to us; and labor in the day.'' The entire time during which they worked is referred to as ''day,'' which proves that the day begins at daybreak.

MISHNA: Although it is preferable to fulfill a particular day’s mitzva at the earliest possible hour, the entire day is a valid time for reading the Megilla; for reciting hallel; for sounding the shofar on Rosh HaShana; for taking the lulav and the other species on Sukkot; for the additional prayer recited on Shabbat and other occasions; and for the additional offerings sacrificed in the Temple on these occasions.

And the entire day is also a valid time for the confession over the bulls brought by the Sanhedrin or by the High Priest to atone for mistakes they had made in their instruction to the people; for the declaration made on the last day of Passover in the fourth and seventh year of the Sabbatical cycle, stating that one’s obligations with regard to tithes have been properly fulfilled (see Deuteronomy 26:12–15); and for the confession of sins made by the High Priest on Yom Kippur over the special offerings brought on that day.

The entire day is also a valid time for placing hands on the head of an offering; for slaughtering an offering; for waving those offerings that require waving in the Temple; for bringing meal-offerings near to the altar; for scooping out a fistful of flour from a meal-offering in order to burn it on the altar; and for burning the fistful of flour on the altar; for pinching the necks of the turtledoves and young pigeons sacrificed as offerings in the Temple; and for receiving the blood of an offering in a vessel; and for sprinkling blood on the altar and on the curtain separating between the Holy and the Holy of Holies.

And the entire day is also a valid time for giving a woman suspected by her husband of having been unfaithful [sota] to drink from the bitter waters (see Numbers 5:11–31); for breaking the neck of the heifer as part of the procedure followed when a corpse is found outside a town and it is not known who caused his death (see Deuteronomy 21:1–9); and for all the steps in the purification process of the leper (see Leviticus 14:1–20).

Correspondingly, all the mitzvot that must be performed at night may be performed anytime during the night: The entire night is a valid time for reaping the omer of barley on the night following the first day of Passover, for burning the fats of offerings that had been brought during the preceding day, and for burning the limbs of burnt-offerings. This is the principle: Something that it is a mitzva to perform during the day is valid if performed anytime during the entire day; something that it is a mitzva to perform at night is valid if performed anytime during the entire night.

GEMARA: The Gemara asks: From where do we derive that these mitzvot were commanded to be performed specifically during the day? With regard to reading the Megilla, the verse states: ''That these days should be remembered and kept'' (Esther 9:28). For reciting the hallel, the proof is from that which is written in hallel: ''From the rising of the sun to its setting, the Lord’s name is to be praised'' (Psalms 113:3). Rabbi Yosei said: The proof is from another verse in hallel: ''This is the day that the Lord has made'' (Psalms 118:24), implying that it is to be recited during the day and not at night.

And daytime is the time for taking the lulav, as it is written: ''And you shall take for yourselves on the first day the fruit of a beautiful tree, branches of a date palm, and boughs of a dense-leaved tree, and willows of the brook'' (Leviticus 23:40). Daytime is also the time for sounding the shofar, as it is written: ''It is a day of sounding the shofar to you'' (Numbers 29:1). Likewise, the time for the additional offerings is day, as it is written with regard to these offerings: ''To sacrifice an offering made by fire to the Lord, a burnt-offering, and a meal-offering, a sacrifice, and libations, each on its own day'' (Leviticus 23:37). And this is also so for the additional prayer, because the Sages made it equivalent to those additional offerings.

And daytime is the time for the confession over the bulls, as this is derived by way of a verbal analogy between one instance of atonement in this context and another instance of atonement in the context of Yom Kippur. As it is taught in a baraita with regard to Yom Kippur, the verse states: ''And Aaron shall present the bull of the sin-offering that is his, and atone for himself and for his household'' (Leviticus 16:11). The verse speaks of atonement achieved through words, i.e., the atonement here is not referring to the sacrifice of offerings and the sprinkling of blood, but rather to atonement achieved through confession. And the atonement of Yom Kippur is only during the day, as it is written: ''For on that day will He atone for you'' (Leviticus 16:30). Just as the atonement on Yom Kippur must take place during the day, so must the other cases of atonement, over other bulls brought as sin-offerings, take place during the day.

And daytime is the time for the declaration with regard to tithes, as it is written in the formula of this declaration: ''And you shall say before the Lord your God, I have removed the sacred things out of my house'' (Deuteronomy 26:13–15); and juxtaposed to that passage it is written: ''This day the Lord your God has commanded you to do'' (Deuteronomy 26:16), implying during the day and not at night.

For placing hands on the head of an offering and for slaughtering an offering, it is derived as it is written: ''And he shall lay his hand upon the head of his offering, and slaughter it'' (Leviticus 3:8), comparing the laying of hands to slaughtering. And it is written with regard to slaughtering: ''On the day that you slaughter'' (Leviticus 19:6), meaning during the day and not at night. And for waving the offerings that require waving, it is derived as it is written: ''And on the day you wave the omer'' (Leviticus 23:12).

And with regard to bringing the meal-offerings near the altar, it is likened to waving, as it is written: ''And the priest shall take the meal-offering of jealousy from the woman’s hand, and shall wave the offering before the Lord, and sacrifice it upon the altar'' (Numbers 5:25). The words ''sacrifice it'' are referring to bringing the offering near the altar. And for scooping out a fistful of flour, and for pinching the necks of the bird-offerings, and for burning the fistful of flour on the altar, and for sprinkling the blood, these are derived as it is written: ''This is the law of the burnt-offering, of the meal-offering, and of the sin-offering, and of the guilt-offering, and of the consecration-offering, and of the sacrifice of the peace-offering; which the Lord commanded Moses on Mount Sinai on the day that he commanded the children of Israel to present their offerings'' (Leviticus 7:37–38).

And with regard to giving the sota to drink from the bitter waters, this is derived from a verbal analogy between one instance of the word ''Torah'' and another instance of the word ''Torah.'' It is written here with respect to a sota: ''And the priest shall execute upon her all this Torah'' (Numbers 5:30), and it is written there with regard to judgment: ''According to the Torah, which they shall teach you, and according to the judgment, which they shall tell you'' (Deuteronomy 17:11).