Hazrat Abu Abdur Rahman Salmi says that every morning an angel comes to you with a white record of deeds and has goodness written in it. When the sun rises, the angel departs for his need, and when you perform the Asr prayer, he has goodness written in it. Thus, if there is goodness at the beginning and end of the record of deeds, it is hoped that the goodness of these two parts will suffice for the middle part as well.