At that time, at mealtime, the World Honored One put on his robe, took up his bowl, and entered the great city of Sravasti to beg for food. After he had finished his sequential begging within the city, he returned, ate the food, put away his robe and bowl, washed his feet, arranged his seat, and sat down.

At that time has five meanings:

1.  It was the time when the Buddha wanted to speak, began to speak, and was speaking.
2. It was the time which breaks up the views of outside ways. Some outside ways deny the existence of past, present, and future, “At that time” means the explanation has occurred in the past, is occurring in the present, and will occur in the future. These words therefore separate the Buddhadharma from the dharma of outside ways.
3. It was the time of planting seeds. Seeds that are planted and nourished will grow. Uncultivated seeds will perish. If one has developed good causes in past lives, but does not cultivate that fruit further in this life, he will have roots that wither and die. If these good roots are continually cared for, they will bear further fruit. So if you have roots that are sufficiently good to allow you to hear sutra lectures, do not just come occasionally; come as often as possible. The more you come, the deeper your roots will grow.
4. It was the time to listen to sutras. That does not mean just listening once or twice. It means listening regularly, for the more you hear the more you understand. In listening to sutras three conditions must be fulfilled: a) a true teacher, b) a true teaching, and c) true study. With only one or two of these conditions fulfilled, study is useless. For instance, if you have a true teaching and truly study, but lack a true teacher, then you cannot understand that teaching. All three conditions must be met for cultivation to succeed.
5. It was the time when the Buddha wanted to speak the dharma and beings wanted to listen. The Buddha wished to speak in the way living beings wanted to hear. The Buddha and living beings are not two, one high and the other low. They are equal.