Shama-il Tirmidhi Chapter 040, Hadith Number 007 (278).

'Abdullah bin Saa-ib Radiyallahu'Anhu reports: "Rasulullah Sallallahu 'Alayhi Wasallam performed four rak'ahs after zawaal before the zuhr salaah, and used to say: 'The doors of the heavens open at this moment. I like that a good deed of mine ascend there at this moment'".

Commentary
What deed can there be more pious and better than salaah, as this is the best among all devotions. Sayyidina Rasulullah Sallallahu 'Alayhi Wasallam has said: "The coolness of my eye is in salaah". In another hadith it is stated: "The one that performs salaah, is like one having a private conversation with Allah".