Read all Ahadith in the book of sacrifices by sahih al muslim

Jundab b. Sufyan reported: I was with Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) on the day of 'Id al-Adha. While he had not returned after having offered (the Id prayer) and finished it, he saw the flesh of the sacrificial animals which had been slaughtered before he had completed the prayer. Thereupon he (the Holy Prophet) said: One who slaughtered his sacrificial animal before his prayer or our prayer ('Id), he should slaughter another one in its stead, and he who did not slaughter, he should slaughter by reciting the name of Allah.

Jundab b. Sufyan reported: I was with Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) (on the occasion) of 'Id al-Adha. After he had completed the prayer with people, he found that the goats had been slaughtered, whereupon he said: He who slaughtered sacrificial animal before the prayer should slaughter a goat (again) in its stead and he who has not slaughtered he should slaughter it by reciting the name of Allah.

This hadith has been narrated on the authority of al-Aswad b. Qais with the same chain of transmitters.

Jundab al-Bajali reported: I saw Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) observing ('Id) prayer on the Day of Sacrifice (10th of Dhu'l-Hijja) and then delivering a sermon and he said: He who sacrificed the (animal) before offering ('Id) prayer, he should offer again in its stead, and he who did not sacrifice the animal should slaughter it by reciting the name of Allah.

This hadith has been narrated on the authority of Shu'ba through another chain of transmitters.

Al-Bara' reported: My maternal uncle Abu Burda sacrificed his animal before ('Id) prayer. Thereupon Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) said: That is a goat (slaughtered for the sake of) flesh (and not as a sacrifice on the day of Adha). He said: I have a lamb of six months. Thereupon he said: Offer it as a sacrifice, but it will not justify for anyone except you, and then said: He who sacrificed (the animal) before ('Id) prayer, he in fact slaughtered it for his own self, and he who slaughtered after prayer, his ritual of sacrifice became complete and he in fact observed the religious practice of the Muslims.

Al-Bara' b. 'Azib reported that his maternal'uncle Abu Burda b. Niyar sacrificed his animal earlier than the Prophet ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) had sacrificed. Thereupon he said: Apostle of Allah, it is the day of meat and it is not desirable (to have longing for it and not to make use of it immediately), so I hastened in offering my animal as a sacrifice, so that I might feed my family and neighbours and my kith and kin. Thereupon Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) said: Offer again your sacrifice. He said: Messenger of Allah, I have a small milch goat of less than one year, and that is better than two dry goats (from which only) meat (can be acquired). Thereupon he said: That is better than the two animals of sacrifice on your behalf, and the sacrifice of a goat, of less than six months shall not be accepted as a sacrifice on behalf of anyone after your (sacrifice).

Al-Bara' b. 'Azib reported: Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) delivered an address on the day (of Nahr) in which he said: None of you should offer sacrifice of animals until he has completed the ('Id) prayer. Thereupon my maternal uncle said: Messenger of Allah, it is the day of meat, so it is not desirable (to keep my family in the state of longing). The rest of the hadith is the same.

Al-Bara' reported Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) having said: He who observes prayer like our prayer and turns his face towards our Qibla (in prayer) and who offers sacrifices (of animals) as we do, he must not slaughter the (animal as a sacrifice) until he has completed the prayer. Thereupon my maternal uncle said: Messenger of Allah, I have sacrificed the animal on behalf of my son. The Messenger of Allah ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) said: This is the thing in which you have made haste for your family. He said: I have a goat with me better than two goats. Thereupon he said: Sacrifice it for that is the best.

Al-Bara' b. 'Azib reported Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) having said: The first (act) with which we started our day (the day of 'Id-ul Adha) was that we offered prayer. We then returned and sacrificed the animals and he who did that in fact adhered to our Sunnah (practice). And he who slaughtered the (animal on that day before the 'Id prayer), for him (the slaughtering of animal was directed to the acquiring of) meat for his family, and there is nothing of the sort of sacrifice in it. It was Abu Burda b. Niyar who had slaughtered (the animal before the 'Id prayer). He said: I have a small lamb, of less than one year, but better than that of more than a year. Thereupon Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) qaid: Sacrifice it, but it will not suffice (as a sacrifice) for anyone after you.