Halakhah zu Tehillim 72:5

The morning Tamid could be brought starting from dawn (“amud ha-shaḥar,” when the first light appears in the east), and the time for praying Shaḥarit should begin at dawn le-khatḥila. Nonetheless, the Sages said that it is proper to recite the Amida after sunrise (“hanetz ha-ḥama”), as it is written: “They shall revere You along with the sun” (Tehilim 72:5; Berakhot 9b). Be-di’avad, if one recites the Amida after dawn but before sunrise, she fulfills her obligation because she prayed at the time when the morning Tamid offering was brought (SA 89:1; and see Peninei Halakha: Prayer, ch. 11 n. 4). The most praiseworthy time to pray is when the early saints, the “vatikin,” who would recite the Amida at the moment of sunrise to fulfill “They shall revere You along with the sun.”¹There are various opinions about the precise time of amud ha-shaḥar, and they are detailed in Peninei Halakha: Prayer, 11:2 n. 1. As a rule, amud ha-shaḥar is never less than 72 minutes before hanetz ha-ḥama. Meaning, by the time it is 72 minutes before hanetz ha-ḥama, amud ha-shaḥar has definitely already occurred.
It is important to know that the earliest time for all daytime mitzvot, such as shofar blowing and brit mila, is sunrise, because the day is defined by the presence of the sun. However, be-di’avad if such mitzvot are performed from the time of amud ha-shaḥar, one’s obligation is fulfilled, because from a certain standpoint, the day begins from first light (Megilla 20a).

The ideal time for praying the morning Amidah is at sunrise, as it is written: "So they will fear You when the sun shines."¹Psalms 72:5. Nevertheless, if you prayed after day-break, your obligation is fulfilled. The time for prayer continues until the [first] third of the day,²The day is reckoned from sunrise to sunset. Daybreak is approximately an hour and twenty minutes before sunrise. and must not be delayed longer. Nevertheless, if it so happened that you delayed longer, even intentionally, you may pray till noon. Even though the reward is not the same as when you pray at the proper time, you will still be rewarded for praying. If you willfully delayed until noon without praying, you can no longer make up for it, and concerning such a person it is said: "What is crooked cannot be made straight."³Ecclesiastes 1:5. Cases where the delay was unintentional or because of circumstances beyond control, will be discussed in Chapter 21.

The Laws of Prayer [i.e. the Amidah] and its [Proper] Time, containing 8 s'ifim
The time for the morning Tefillah (i.e. Amidah): its commandment is that it should begin with the "blossoming" (i.e. rising) of the sun, as it is written, "They will revere You with the sun (Psalm 72:5)." And if one prayed from the [time of] "the pillar of the morning" (i.e. dawn) and the appearance of the east has become light, one has fulfilled [one's obligation]. And its time continues until the end of four hours which is a third of the daytime. And if one erred or transgressed and prayed after the fourth hour until noon, even though one does not have the [same] reward as praying at its [proper] time, in any case there is still a reward of prayer. Rem"a: And after noon it is forbidden to pray the Tefillah of the morning (Beit Yosef in the name of the Rashba [Rabbi Shlomo ben Adret], Chapter: "Morning Prayer") . And see below, the beginning of Siman 108].