[Excerpted from the Encyclopedia of Islamic Doctrine, Shaykh Muhammad Hisham Kabbani, As-Sunna Foundation of America, 1996]
As for the night of the first Friday of the month of Rajab or its first night, both known as the "Night of wishes" (laylat al-ragha'ib) during which is performed the salat al-ragha'ib, its observance was disapproved by Imam Nawawi in his Sharh al-muhadhdhab and Fatawa as based on invalid (batil) evidence, and this is also the position of al-`Izz ibn `Abd al-Salam. However, the hafiz Ibn al-Salah disagreed with al-`Izz and considered praiseworthy the performance of Salat al-ragha'ib, while `Ali al-Qari said in his Asrar al-marfu`a regarding this:
The hadith: salat al-nahar `ajma' (Prayer in the daytime is silent), even if invalid (batil), nevertheless its meaning is true. The same holds about the hadiths of the prayers they have mentioned concerning honored days and exalted nights such as salat al-ragha'ib -- the most famous example being the prayer of mid-Sha`ban -- because the hadiths concerning them (i.e. the prayers) are not forged but merely weak.30
Finally, Ibn `Abd al-Razzaq narrates in his Musannaf (4:317) that Ibn `Umar said:
There are five nights in which invocation (du`a) is not turned back: the night of Jum`a, the first night of Rajab, the night of mid-Sha`ban, and the two nights of `Eid.