Greatest of Congregations

Ibn al-Qayyim [رحمه الله] said: The Friday prayer is from the greatest of congregations of the Muslims.
The ruler not ruling in an honest manner

I heard the Prophet (ﷺ) saying, “Any man whom Allah has given the authority of ruling some people and he does not look after them in an honest manner, will never feel even the smell of Paradise.”
Abandoning a fellow Muslim

Narrated Abu Aiyub Al-Ansari: Allah’s Messenger (ﷺ) said, “”It is not lawful for a man to abandon his brother Muslim for more than three nights.””
Hitting a Muslim on the face is forbidden

Narrated Abu Huraira: The Prophet (ﷺ) said, If somebody fights (or beats somebody) then he should avoid the face.
From the Sunnahs of Friday

Making Ghusl
Applying Perfume
Offering Friday prayer
Making a lot of du’a
Sending blessings upon the Prophet Muhammad
Reading Surat al-Kahf
Backbiter

Narrated Hudhaifa: I heard the Prophet (ﷺ) saying, “A Qattat will not enter Paradise.”
Commanding good is Sadaqa

Narrated Jabir bin `Abdullah: The Prophet (ﷺ) said, Enjoining, all that is good is a Sadaqa
Abusing a Muslim is Fusuq

Narrated `Abdullah: Allah’s Messenger (ﷺ) said, “”Abusing a Muslim is Fusuq (i.e., an evil-doing), and killing him is Kufr (disbelief).
Skipping Jumu’ah Deliberately

The Prophet (ﷺ) said: He who leaves the Friday prayer (continuously) for three Friday on account of slackness, Allah will print a stamp on his heart.
The pleasure of the Lord

The Prophet said: The Lord’s pleasure is in the parent’s pleasure, and the Lord’s anger is in the parent’s anger.