Why is Surat Al-Yaseen called The Heart of the Quran?

Answer 1

Because:

1. There are some traditions (hadith) stating that this surah is the heart of the Quran. Imam al-Sadiq (alayh es-Salam) is quoted as saying: ان لکل شیء قلبا و ان قلب القرآن یس; all things have heart and the heart of the Quran is Surah Yaseen. (Allameh Majlesi, Bihar al-Anwar, V. 89, p. 288, Sheikh Hurr Ameli, wasa’il, V. 6, p. 247, Saduq, Thawab ul-A’mal, p.111).

2. Surah Yaseen contains all pillars of Islam and because of that is called the heart of the Quran. These pillars include Tawhid (Monotheism), Nabowwat (Prophethood), Adl (Justice), Imamate, Ma’ad.

3. According to traditions, there are ten names for the Prophet Muhammad (s) five of which have been mentioned in the Holy Quran like Ahmad and Muhammad. One of these names and maybe the most mysterious one is Yaseen. Therefore, Surah Yaseen is the surah of the Prophet. (Saduq, Khisal, v. 2, p. 426 & Allameh Majlesi, Bihar al-Anwar, v. 16, p. 96).

Everything has a heart which is its best part and continuity of its life depends on that. The heart of the world is the noblest creation of God who is the Holy Prophet.

The Quranic surahs are words of God. The heart of this book is the surah of the heart of the worlds who is the Holy Prophet (Yaseen).

Answer 2

This is because the Surah is in the exact middle of the Qu'ran. This is why its called the "Heart of the Qur'an."

Your welcome ;)