All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Repeatedly leaving the Friday prayer prevents the heart from receiving the guidance of Allaah The Almighty and causes the person to be apathetic towards performing acts of worship.
There are several authentic Hadeeths affirming this:
1- It was narrated on the authority of Abu Hurayrah and ‘Abdullaah Ibn ‘Umar that the Prophet, sallallaahu ‘alayhi wa sallam, threatened the one who leaves the Friday prayer that Allaah The Exalted would close his heart and thus, he would become one of the heedless. [Muslim]
2- It was narrated on the authority of Abu Al-Ja‘d Adh-Dhamri that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said that whoever misses three consecutive Friday prayers out of negligence will have a seal put over his heart by Allaah The Almighty to prevent it from receiving guidance. [At-Tirmithi]
Scholars interpreted these Hadeeths as follows:
- Al-Haafith Al-‘Iraaqi said that the threat mentioned in these Hadeeths applies to the person who leaves the Friday prayer without a Sharee‘ah approved concession. In such a case, Allaah The Exalted will make his heart like the heart of a hypocrite.
- Shaykh ‘Abdul-Haqq stated that whoever leaves the Friday prayer because he derides it is no longer a Muslim.
- Ibn Al-‘Arabi mentioned that these Hadeeths do not mean that such a person will never be guided to repentance, since there are several other Sharee‘ah texts indicating that Allaah The Almighty accepts the repentance of any sinner; Allaah The Almighty Says (what means): {Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allaah . Indeed, Allaah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful."} [Quran 39:53]
Consequently, you should advise your friend to repent to Allaah The Almighty from that sin. If he does, then you would not be wrong in continuing to be his friend.
Allaah Knows best.