✅Answer: The last two or three nights of the lunar month are called 'muhaq.' During this time, the moon is not visible at night or during the day. This is because it rises during the day, making it hidden and not visible at any time. Some actions are forbidden during this period, as shown by the following narrations:

1 عَنِ الْحَسَنِ بْنِ عَلِیِّ بْنِ یَقْطِینٍ عَنْ یُونُسَ بْنِ عَبْدِ الرَّحْمَنِ عَنْ عَبْدِ اللَّهِ بْنِ سُلَیْمَانَ عَنْ أَحَدِهِمَا قَالَ کَانَ أَبِی إِذَا خَرَجَ یَوْمَ الْأَرْبِعَاءِ مِنْ آخِرِ الشَّهْرِ وَ فِی یَوْمٍ یَکْرَهُهُ النَّاسُ مِنْ مُحَاقٍ أَوْ غَیْرِهِ تَصَدَّقَ بِصَدَقَةٍ ثُمَّ خَرَجَ

📚 Mahasin, Vol. 2, p. 348

Imam Baqir, peace be upon him, or Imam Sadiq, peace be upon him, said: When my father would travel on the last Wednesday of the month and on days that people consider inauspicious, such as the muhaq or other days, he would first give some charity and then travel.

2 عَنْ مُحَمَّدِ بْنِ أَحْمَدَ السِّنَانِیِّ عَنْ مُحَمَّدِ بْنِ أَبِی عَبْدِ اللَّهِ الْکُوفِیِّ عَنْ سَهْلِ بْنِ زِیَادٍ عَنْ عَبْدِ الْعَظِیمِ بْنِ عَبْدِ اللَّهِ الْحَسَنِیِّ عَنْ عَلِیِّ بْنِ مُحَمَّدٍ الْعَسْکَرِیِّ عَنْ آبَائِهِ فِی حَدِیثٍ قَالَ مَنْ تَزَوَّجَ وَ الْقَمَرُ فِی الْعَقْرَبِ لَمْ یَرَ الْحُسْنَی وَ قَالَ مَنْ تَزَوَّجَ فِی مُحَاقِ الشَّهْرِ فَلْیُسَلِّمْ لِسِقْطِ الْوَلَدِ

📚 Illal al-Shara'i, Vol. 2, p. 514

Imam Baqir, peace be upon him, said in a hadith: Whoever marries when the moon is in the constellation of Scorpio will not see goodness or well-being. And he said: Whoever marries (performs the marriage contract) during the muhaq of the month should expect a miscarriage. (He will be afflicted with a miscarriage.)

3 مُحَمَّدُ بْنُ یَعْقُوبَ عَنْ عِدَّةٍ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ خَالِدٍ عَنْ بَکْرِ بْنِ صَالِحٍ عَنْ سُلَیْمَانَ بْنِ جَعْفَرٍ الْجَعْفَرِیِّ عَنْ أَبِی الْحَسَنِ قَالَ مَنْ أَتَی أَهْلَهُ فِی مُحَاقِ الشَّهْرِ فَلْیُسَلِّمْ لِسِقْطِ الْوَلَدِ

📚 Kafi, Vol. 5, p. 499

Imam Kadhim, peace be upon him, said: Whoever has intercourse with his wife during the muhaq of the month should expect and be prepared for a miscarriage.

4 بِإِسْنَادِهِ عَنْ أَبِی سَعِیدٍ الْخُدْرِیِّ فِی وَصِیَّةِ النَّبِیِّ صلی الله علیه و آله لِعَلِیٍّ أَنَّهُ قَالَ یَا عَلِیُّ لَا تُجَامِعْ أَهْلَکَ فِی آخِرِ دَرَجَةٍ إِذَا بَقِیَ یَوْمَانِ فَإِنَّهُ إِنْ قُضِیَ بَیْنَکُمَا وَلَدٌ یَکُونُ عَشَّاراً وَ عَوْناً لِلظَّالِمِینَ وَ یَکُونُ هَلَاکُ فِئَامٍ مِنَ النَّاسِ عَلَی یَدِهِ

📚 Man La Yahduruhu al-Faqih, Vol. 3, p. 553

The Messenger of Allah, peace and blessings be upon him, said in a hadith to Amir al-Mu'minin, peace be upon him: O Ali; do not have intercourse with your wife when the moon is in its last degree, when two days of the month remain, because if a child is conceived between you, he will be a tax collector and an assistant to the oppressors, and the destruction of a group of people will be at his hands!

5 کَانَ أَمِیرُ الْمُؤْمِنِینَ علیه السلام یَکْرَهُ أَنْ یُسَافِرَ الرَّجُلُ أَوْ یَتَزَوَّجَ وَ الْقَمَرُ فِی الْمُحَاقِ.

📚 Bihar al-Anwar, Vol. 59, p. 54

Amir al-Mu'minin, peace be upon him, disliked a person to travel or marry when the moon is in the muhaq!

✅Other days have also been forbidden for this matter in the narrations of the Ahl al-Bayt, peace be upon them, such as the first night and the middle night of the month, Wednesday nights, the night of Eid al-Fitr, and the night of Eid al-Adha... which are of great importance. While learning their hadiths and acting upon them, one should strive to teach the relevant narrations to Muslims, as unfortunately, many people are unaware of them and as a result, face many problems. Of course, acting upon these narrations requires knowledge of the beginning and end of the lunar month, so we must be diligent in sighting the new moon for all months and also look for the muhaq of the month at its end.

✅It is worth noting that at the end of the lunar month and to determine the muhaq, the moon can only be seen in the east for a few minutes after the break of dawn until before sunrise. If the moon is not seen at that time, it indicates that the moon is in the muhaq, which usually begins on the 28th night of the lunar month and lasts for 2 nights if the month has 29 days and 3 nights if the month has 30 days.