Why is Al-Fatihah Chapter called the Seven of Al-Mathani (the seven repeatedly recited verses)?

Answer

Praise Be to Allah and Peace Be Upon His Messenger.

This chapter is called the Seven of Al-Mathani as it is given this name in the Holy Qur’an. Allah says addressing His Messenger Muhammad (PBUH): “And indeed, We have bestowed upon you seven of Al‑Mathani (seven repeatedly recited Verses), (i.e. Surat Al‑Fatihah) and the Grand Qur’ān.” (Al-Hijr: 87).

Abu Sa’id ibn Al-Mu’alla narrated: “While I was praying in the Mosque, Allah's Messenger (PUBH) called me but I did not respond to him. Later I said, "O Allah's Messenger! I was praying." He said, "Didn't Allah say: "Give your response to Allah (by obeying Him) and to His Apostle when he calls you." (8.24) He then said to me, "I will teach you a Sura which is the greatest Sura in the Qur'an, before you leave the Mosque." Then he got hold of my hand, and when he intended to leave (the Mosque), I said to him, "Didn't you say to me, 'I will teach you a Sura which is the greatest Sura in the Qur'an?' He said, "Al-Hamdu-Li l-lah Rabbi-l-`alamin (i.e. Praise be to Allah, the Lord of the worlds) which is Al-Sab'a Al-Mathani (i.e. seven repeatedly recited Verses) and the Grand Qur'an which has been given to me."

Thus, Al-Fatihah Chapter is called the Seven of Al-Mathani because its verses are seven, and because the one who prays keeps repeating it in every Rak’ah, and because he praises Allah while reciting it.