All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.

The Qunut supplication in Fajr prayer is a confirmed Sunnah according to the narration of Anas (may Allah be pleased with him), who reported that the Prophet Mohammad (peace be upon him) used to recite Qunut in the Fajr prayer until he left this world. This narration is reported by Imam Ahmad. Sheikh al-Islam al-Nawawi, may Allah have mercy on him, mentioned: "Qunut is recommended for us in the Fajr prayer, and it is a confirmed Sunnah. If someone leaves it, his prayer is still valid, but if he intentionally leaves it, he should perform Sujood as-Sahw (prostration for forgetfulness), and the same applies if he leaves it forgetfully" [Al-Adhkar, Vol. 1/P. 59].

Regarding the duration of Qunut according the Shafi'i school of thought, the default principle is that it should be done with moderation. This is because the entire congregational prayer is based on moderation, and any part of it should follow the same principle. Additionally, Qunut is linked to the first Tashahhud in the sense that it takes the same ruling.

In the Shafi'i madhhab, extending the Qunut excessively is considered contrary to the Sunnah. Some even argue that it may invalidate the prayer, as it involves prolonging a short obligatory act (standing up from Ruku`), which is against the principle of moderation in prayer. However, the relied-upon opinion in the Shafie madhhab is that the prayer remains valid, although the elongation is disliked. Al-Bajuri, a Shafi'i scholar, mentioned, "It is disliked to add to it (referring to the first Tashahhud) due to its foundation on moderation... and it is disliked to prolong Qunut similar to the first Tashahhud" [Hashiyat al-Bajuri, Vol. 1/P. 445].

Moderating the supplication in Qunut is consistent with what is narrated from the Prophet Mohammad (peace be upon him). The supplication in Qunut is brief and light. The Prophet (peace be upon him) said: "O Allah, guide me among those whom You have guided, pardon me among those You have pardoned, turn to me in friendship among those on whom You have turned in friendship, and bless me in what You have bestowed, and save me from the evil of what You have decreed. For verily You decree and none can influence You; and he is not humiliated whom You have befriended. Blessed are You, O Lord, and Exalted." (Reported by Abu Dawood). It is preferable to limit the supplication in Qunut to what is established in the Sunnah, even though any supplication, including verses from the Quran that contain supplications, would be valid for Qunut. However, the preferable practice is what is authentically reported from the Prophet (peace be upon him). Imam al-Nawawi mentioned: "In Qunut, any supplication is valid according to the reliable opinion in the Shafi'i school. If one supplicates with a verse or verses from the Quran that include a supplication, Qunut is valid. However, what is authentically reported from the Sunnah is better" [Al-Adhkar, Vol. 1/P. 61].

It is recommended to combine between two supplications during Qunut: the first being the supplication reported from the Prophet Mohammad (peace be upon him), and the second being the supplication reported from Umar ibn al-Khattab (may Allah be pleased with him). The latter is specifically recommended for the individual and for a congregational prayer with those who agree to prolong the Qunut, not with the intention of elongation but to achieve the virtue of combining the authentic supplication from the Prophet (peace be upon him) with the supplication of Umar ibn al-Khattab.

The supplication of Umar ibn al-Khattab includes: "O Allah, we seek Your help, seek Your forgiveness, seek guidance from You, rely on You, believe in You, entrust our affairs to You, and praise You for all the good. We thank You and do not disbelieve in You. We cast off and forsake those who disobey You. O Allah, You alone we worship, and to You, we pray and prostrate, and to You, we strive and hasten. We hope for Your mercy and fear Your punishment. Indeed, Your punishment is due upon the disbelievers. O Allah, punish the disbelievers from the People of the Book who obstruct Your path, deny Your messengers, and fight against Your allies. O Allah, forgive the believing men and women, the Muslim men and women, repair their relationships, unite their hearts, and instill in their hearts faith and wisdom. Make them steadfast on the path of Your Messenger, and grant them the ability to fulfill the covenant they made with You. Support them against their enemies and Your enemies, the Lord of Truth. And make us among them" (Reported by al-Bayhaqi). Imam al-Nawawi mentioned, "It is recommended to send blessings upon the Prophet (peace be upon him) after the supplication" [Al-Majmu', Vol. 3/P. 493].

In conclusion, it is disliked for the imam to prolong the Qunut, and it is recommended for him to limit it to the supplications that are authentically reported. However,  if he extends his prayer, it remains valid but this is dislike. And Allah the Almighty knows best.