✅ Answer: Please pay attention to the following narrations:

1 عن أَبِي عبداللَّه قال: إِذَا غَرَبَتِ الشَّمْسُ فَقَدْ دَخَلَ وَقْتُ الصَّلَاتَيْنِ إِلَى نِصْفِ اللَّيْلِ إِلَّا أَنَّ هَذِهِ قَبْلَ هَذِهِ و إِذَا زَالَتِ الشَّمْسُ فَقَدْ دَخَلَ وَقْتُ الصَّلَاتَيْنِ إِلَّا أَنَّ هَذِهِ قَبْلَ هَذِهِ

📚 Tahdhib Vol. 2, p. 27

Imam Sadiq (peace be upon him) said: When the sun sets, the time for both the Maghrib and 'Isha prayers has entered, except that the Maghrib prayer is before the 'Isha prayer, and when the sun passes its zenith, the time for the two Dhuhr and 'Asr prayers has entered, except that the Dhuhr prayer is before the 'Asr prayer!

2️⃣ Imam Sadiq (peace be upon him) said: When the sun passes its zenith, the time for the Dhuhr prayer has entered until a worshipper can perform four rak'ahs of prayer, and when this time has passed, the common time for the Dhuhr and 'Asr prayers enters until there remains from the sun what is enough for a worshipper to perform four rak'ahs, so when this amount of time remains, the time for the Dhuhr prayer has ended and the time for the 'Asr prayer remains until the sun sets!

📚 Tahdhib Vol. 2, p. 25

3️⃣ From Abi 'Abdillah, he said: When the sun sets, the time for the Maghrib prayer has entered until an amount of time passes for a worshipper to perform three rak'ahs of prayer. When that amount has passed, the common time for the Maghrib and 'Isha' al-Akhira prayers has entered until there remains from the middle of the night an amount of time for a worshipper to perform four rak'ahs. And when that amount remains, the time for the Maghrib prayer has exited and the time for the 'Isha' al-Akhira prayer remains until the middle of the night.

📚 Tahdhib Vol. 2, p. 28

Imam Sadiq (peace be upon him) said: When the sun sets, the time for the Maghrib prayer has entered until an amount of time passes for a worshipper to perform three rak'ahs of prayer. When that amount has passed, the common time for Maghrib and 'Isha has entered until there remains to the middle of the night an amount of time for a worshipper to perform four rak'ahs. When that amount remains, the time for the Maghrib prayer has exited and the time for the 'Isha prayer remains until the middle of the night!

4 عَنْ زُرَارَةَ عَنْ أَبِي جَعْفَرٍ قَالَ:.. فَإِنْ كُنْتَ قَدْ صَلَّيْتَ الْعِشَاءَ الْآخِرَةَ وَ نَسِيتَ الْمَغْرِبَ فَقُمْ فَصَلِّ الْمَغْرِبَ

📚 Al-Kafi Vol. 3, p. 291

In a hadith, Imam Baqir (peace be upon him) said: If you performed the 'Isha prayer and forgot the Maghrib prayer, stand up and perform the Maghrib prayer!

5 عَنِ الْحَلَبِيِّ قال: سَأَلْتُهُ عَنْ رَجُلٍ نَسِيَ أَنْ يُصَلِّيَ الْأُولَى حَتَّى صَلَّى الْعَصْرَ قَالَ فَلْيَجْعَلْ صَلَاتَهُ الَّتِي صَلَّى الْأُولَى ثُمَّ لْيَسْتَأْنِفِ الْعَصْر

📚 Tahdhib Vol. 2, p. 269

Halabi said: I asked the Imam (peace be upon him) about a person who forgets to perform the Dhuhr prayer until he performs the 'Asr prayer; the Imam said: He should consider the prayer he performed as the Dhuhr prayer and perform the 'Asr prayer from the beginning!

✅ Based on the above narrations and others, with the sun's passing of its zenith, the time for both the Dhuhr and 'Asr prayers has entered, but it is obligatory to perform the Dhuhr prayer before the 'Asr prayer. Therefore, from the beginning of the sun's passing of its zenith, an amount of time for four rak'ahs of prayer is allocated to the Dhuhr prayer, and similarly, when the sun sets, the time for both the Maghrib and 'Isha prayers has entered, but it is obligatory to first perform the Maghrib prayer and then the 'Isha prayer, and therefore, from the beginning of sunset, an amount of time for three rak'ahs of prayer is allocated to the Maghrib prayer.

Now, if someone forgets to perform the Dhuhr prayer first and performs the 'Asr prayer, and then remembers that they did not perform the Dhuhr prayer and the prayer time is still remaining, they should consider the prayer they performed as the Dhuhr prayer and perform the 'Asr prayer from the beginning, and there is no need to perform both prayers again.

But if someone forgets to perform the Maghrib prayer until they perform the 'Isha prayer and then realize that they did not perform the Maghrib prayer, they should stand up and perform the Maghrib prayer, and there is no need to perform the 'Isha prayer again.

✅ In a situation where a person realizes after the 'Asr prayer that their Dhuhr prayer was invalid and needs to be repeated, or after the 'Isha prayer they realize that their Maghrib prayer was invalid and needs to be repeated, even if the prayer time is still remaining, no narration has been received that obliges the repetition of both prayers. Performing the Dhuhr prayer or the Maghrib prayer is sufficient, because no instruction has been received to repeat the 'Asr prayer after repeating the Dhuhr prayer, or to repeat the 'Isha prayer after repeating the Maghrib prayer in this situation. It is only in the normal situation that a person cannot perform the 'Asr prayer before Dhuhr and the 'Isha prayer before Maghrib.