In this verse Allah asks the prophet to be patient and to ask for Allah’s forgiveness and to praise Him at various times during the day.
So be patient (O Muhammad). Verily, the Promise of Allah is true, and ask forgiveness for your fault and glorify the praises of your Lord in the ‘Ashi (i.e. the time period after the mid noon till sunset) and in the Ibkar (i.e. the time period from early morning or sunrise till before mid noon) [it is said that, that means the five compulsory congregational Salat (prayers) or the ‘Asr and Fajr prayers].
Quran (Surah Al-Ghafir, Verse 55)