✅Answer: Please pay attention to the following narrations:

1 مُحَمَّدُ بْنُ يَعْقُوبَ عَنْ مُحَمَّدِ بْنِ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْحُسَيْنِ بْنِ سَعِيدٍ عَنْ فَضَالَةَ عَنْ أَبَانٍ عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي عَبْدِ اللَّهِ قَالَ: سَأَلْتُ أَبَا عَبْدِ اللَّهِ عَنِ الرَّجُلِ يَسْجُدُ وَ عَلَيْهِ الْعِمَامَةُ لَا يُصِيبُ وَجْهُهُ [جَبهته] الْأَرْضَ قَالَ لَا يُجْزِيهِ ذَلِكَ حَتَّى تَصِلَ جَبْهَتُهُ إِلَى الْأَرْضِ

📚 Al-Kafi, Vol. 3, p. 334

Translation: Abd al-Rahman ibn Abi Abdillah said: I asked Imam Sadiq (peace be upon him) about a person who prostrates while wearing a turban and his forehead does not reach the ground; the Imam said: It is not sufficient for him until he makes his forehead reach the ground.

2 عَنْ زُرَارَةَ عَنْ أَحَدِهِمَا أَنَّهُ قَالَ: قُلْتُ لَهُ الرَّجُلُ يَسْجُدُ وَ عَلَيْهِ قَلَنْسُوَةٌ أَوْ عِمَامَةٌ فَقَالَ إِذَا مَسَّ شَيْ ءٌ مِنْ جَبْهَتِهِ الْأَرْضَ فِيمَا بَيْنَ حَاجِبَيْهِ وَ قُصَاصِ شَعْرِهِ فَقَدْ أَجْزَأَ عَنْهُ

📚 Faqih, Vol. 1, p. 271

Translation: Zurarah said: I said to Imam Sadiq or Imam Baqir (peace be upon them): A person prostrates while a hat or turban is on his head. The Imam said: When a part of his forehead, the area between the hairline and the two eyebrows, reaches the ground, it is sufficient for him.

3 عَنْ عَلِيِّ بْنِ جَعْفَرٍ عَنْ مُوسَى بْنِ جَعْفَرٍ قَالَ: سَأَلْتُهُ عَنِ الرَّجُلِ يَسْجُدُ فَتَحُولُ عِمَامَتُهُ وَ قَلَنْسُوَتُهُ بَيْنَ جَبْهَتِهِ وَ بَيْنَ الْأَرْضِ قَالَ لَا يَصْلُحُ حَتَّى يَضَعَ جَبْهَتَهُ عَلَى الْأَرْضِ

📚 Qurb al-Isnad, p. 92

Translation: Ali ibn Ja'far said: I asked Musa ibn Ja'far (peace be upon him) about a person who prostrates and his turban or hat comes between his forehead and the ground; the Imam said: This is not correct until he places his forehead on the ground.

4 عَنْ زُرَارَةَ عَنْ أَبِي جَعْفَرٍ قَالَ: الْجَبْهَةُ كُلُّهَا مِنْ قُصَاصِ شَعْرِ الرَّأْسِ إِلَى الْحَاجِبَيْنِ مَوْضِعُ السُّجُودِ فَأَيُّمَا سَقَطَ مِنْ ذَلِكَ إِلَى الْأَرْضِ أَجْزَأَكَ مِقْدَارُ الدِّرْهَمِ أَوْ مِقْدَارُ طَرَفِ الْأَنْمُلَةِ.

📚 Al-Kafi, Vol. 3, p. 333

Translation: Imam Baqir (peace be upon him) said: The entire forehead from the hairline to the two eyebrows is the place of prostration, so whatever amount of this area reaches the ground is sufficient for you:

The size of a dirham

Or the size of a fingertip

5 عَنْ زُرَارَةَ عَنْ أَبِي جَعْفَرٍ قَالَ: سَأَلْتُهُ عَنْ حَدِّ السُّجُودِ قَالَ مَا بَيْنَ قُصَاصِ الشَّعْرِ إِلَى مَوْضِعِ الْحَاجِبِ مَا وَضَعْتَ مِنْهُ أَجْزَأَكَ.

📚 Al-Tahdheeb, Vol. 2, p. 85

Translation: Zurarah said: I asked Imam Baqir (peace be upon him) about the limit of prostration; the Imam said: Between the hairline and the eyebrows (is the place of prostration), so whatever amount of this area you place on the (prayer stone and ground) is sufficient for you.

✅ It is clearly apparent that it is necessary to make a part of the forehead touch the ground or something on which prostration is valid, and a complete barrier of a chador, hat, turban, or other thing between the forehead and that on which prostration is valid, is not correct and invalidates the prostration and the prayer.

✅ According to the above narrations, if a part of the forehead, for example, the size of a dirham or the size of a fingertip, reaches the prayer stone, it is sufficient.

✅ In the hadith in 📚 Al-Tahdheeb, Vol. 2, p. 298, it is narrated from Imam Sadiq (peace be upon him) that prostrating with the entire forehead is more virtuous.