Wearing a cap in Salaat

 To cover the head, using a turban or wearing a skull cap (Topi) is Sunnah.  The Holy Prophet (Sallallahu alaihi wa sallam) would tie a turban on the cap.  Imam Haithami has established a chapter on "Topi" in his book of Hadith Majma Uz Zawaaid and has recorded a Hadith on the authority of Tabarani:

 

Translation of Hadith:  It has been narrated on the authority of Hadhrat Abdullah bin Umar (May Allah be well pleased with them) that the Holy Prophet (Sallallahu alaihi wa sallam) would wear a white cap.  (Majma Uz Zawaaid, Vol. 5, Pg No. 121)

 

There is a Hadith in Jame' Tirmidhi:

 

Translation of Hadith:  Indeed! The difference between us and the "Mushrikeen" (those who take partners with Allah Ta'ala) is turbans tied on caps.  (Jame' Tirmidhi, Vol. 1, Pg No. 308)

 

Thus, the cap (Topi) is mentioned in the Hadith and we learn that in the blessed era of the Holy Prophet (Sallallahu alaihi wa sallam), caps were very common and specially for Salaat, turbans were also worn, as given in Sahih Bukhari:

 

Translation of Hadith:  The great Tabi'ee Hadhrat Hasan Basri (May Allah be well pleased with him) says: Because of the heat, the Sahabah, would perform Sajdah on their caps and turbans and their hands would be in their sleeves.   (Sahih Bukhari, Vol. 1, Pg No. 56)

 

There is another Hadith, the Holy Prophet (Sallallahu alaihi wa sallam) was asked about the clothes of Ihram and He (Sallallahu alaihi wa sallam) said:

 

Translation of Hadith:  You should not wear tunics (Kameez in Urdu), nor pajamas, neither turbans nor caps.....  (Sahih Bukhari, Vol. 1, Pg No. 248, Hadith No: 1838)

 

This Hadith shows that the Sahabah would generally wear turbans and caps, that is why the Holy Prophet (Sallallahu alaihi wa sallam) stopped them from wearing them in Ihram. 

 

Thus, the Masnoon and Mustahab (Established by the Sunnah and the Commendable) way is that Salaat should be offered with the head covered.  Not doing because of laziness is Makruh (undesirable), as given in Durre Mukhtaar, Vol. 1, Pg No. 474 and Raddul Muhtaar, Vol. 1, Pg No. 474:

 

Translation of Hadith:  Offering Salaat with the head uncovered is Makruh.  It is very bad that covering the head should be considered a chore because of laziness and not to consider it an important act in Salaat and to drop it.