Shama-il Tirmidhi Chapter 040, Hadith Number 006 (277).

Abu Ayyub Ansaari Radiyallahu'Anhu says. "Rasulullah Sallallahu 'Alayhi Wasallam always performed four rak'ahs after the time of za'waal. I said: 'O Messenger of Allah. You give much importance to these four rak'ahs after the zawaal of the sun?' Rasulullah Sallallahu 'Alayhi Wasallam replied: 'The doors of the skies open from the zawaal of the sun till the zuhr salaah is performed. I desire that a good deed of mine reaches the skies at that time'. I asked: 'Is there a recital in every rak'ah?' He replied: 'Yes'. I enquired: 'Should salaam be made at the end of two rak'ahs?' Rasulullah Sallallahu 'Alayhi Wasallam replied 'No' (Salaam should be made only at the end of four rak'ahs)".

Commentary
The sufis name this salaah as salaatuz zawaal, and this is included in the mustahab prayers. According to the majority of the muhadditheen this is the four sunan of zuhr salaah. The reason being, besides the sunan of zuhr, there is no other nafl prayer after zawaal (midday) that Sayyidina Rasulullah Sallallahu 'Alayhi Wasallam performed regularly. In both cases according to both sayings this hadith and the ensuing one has no apparent relevance with the salaatut duha.

It is perplexing that Imaam Tirmidhi has mentioned this hadith in this chapter. The mashaa-ikh have given a few explanations regarding this. The first is that this was the ending time for chast, therefore it was naturally included here, and a separate chapter was not created. Some are of the opinion that this is due to an error committed by the copier (calligrapher), which resulted in this being mentioned here. Otherwise its original place was in the previous chapter. It is said that in a few copies of this kitaab, this hadith is mentioned under the previous chapter, and not in this chapter. Some have given other explanations too.