"One evening Isaac went out to the field to think." This must have been a long time after the servant and Rebekah left her home since they had to travel a long distance.
The word "behold" here alerts us to pay attention to the surprising information that follows. "When he looked up he was surprised to see camels coming"
"So she covered her face with her veil." This is a sign of respect and modesty towards the man she will marry. The full meaning of this can be made explicit. (See: [[rc://en/ta/man/translate/translate-symaction]] and [[rc://en/ta/man/translate/figs-explicit]])