Fridays and Thursday nights represent the climax of devotional acts during the week. In addition to the daily devotional practices, Friday represents the climax of devotional acts.
Gradation and acceleration of the devotional rate is a method largely used by Islam. With regard to daily worship, acceleration of devotional acts begins at night and in the period of the early dawn up to the time of the obligatory dawn prayer. With regard to weekly worship, this process begins on Thursday night and continues up to the afternoon congregational prayer on Friday.
With regard to monthly worship, the apogee lies within the nights of the full moon (i.e. 13th, 14th, and 15th of the month according to the Islamic lunar calendar). With regard to yearly worship, this process hits its peak in the month of Ramadhan although it starts at the beginning of Rajab.
With regard to the devotional acts in the month of Ramadhan, this process is at its highest during its last ten nights, especially the nights of Qadr, and ends on the night before ‘«d al-Fitr.
There is a supplication for each day of the week. These supplications are reported from Imam Zayn al-’Abidin (‘a). They contain highly regarded contents and the name of the day to which it is dedicated. These supplications, again, can be found in some versions of the book al-Sahifah al-Sajjadiyyah and Shaykh al-Qummi’s Mafatih al-Jinan.
Shaykh al-Tusi, in his book of Misbah al-Mutahajjid, has reported from the Holy Prophet (S) (or on the authority of Anas), a number of recommended prayers for each day of the week except Friday.
As to Sayyid Ibn Tawus, he has reported—in his book of Jamal al-Usbu’ through a chain of authority extending to Imam al-Hasan al-Askari (‘a)—a number of prayers for each day of the week. The majority of these prayers and a number of the previously mentioned ones have been reported by Shaykh al-Kaf’ami in his book of al-Misbah.1
Shaykh al-Tusi, in the same abovementioned book, has reported, although without mentioning the chain of authority, a number of prayers whose rewards are dedicated to the Holy Prophet (S) and the other Infallibles (‘a). Each prayer is offered on each day of the week and then dedicated to each one of the Holy Infallibles (‘a) respectively. These prayers spread over the days of two weeks.2