Shaykh Saalih ibn Fawzaan (may Allah preserve him) was asked: What is the ruling on sending text messages every Friday and ending with the phrase “Jumu‘ah mubaarak”?
He replied: The early generation did not congratulate one another on Fridays, so we should not introduce anything that they did not do.
A similar fatwa was issued by Shaykh Sulaymaan al-Maajid (may Allah preserve him), when he said:
We do not think it is prescribed to exchange congratulations on Fridays, such as saying to one another, “Jumu‘ah mubaarak” and so on, because it comes under the heading of du‘aa’s and dhikrs, which must be based on a text (of the Qur’aan or Sunnah) because this is purely the matter of worship and if it were good, the Prophet (blessings and peace of Allah be upon him) and his Companions (may Allah be pleased with them) would have done it before us. If anyone suggests that this is permissible, then that may imply that it is prescribed to say du‘aa’s and congratulate one another after having done the five daily prayers and other acts of worship, and du‘aa’ at these times was not done by the early generations.
I’ve attempted to edit and delete anywhere I have used “Jummah Mubarak” on this forum in my posts after seeing this ruling as I didn’t realize at the time I posted them. Astaghfirullah.