“your brother.” Abimelech here calls Abraham “your brother” as a sarcastic rebuke to both Abraham and Sarah.

“a covering of the eyes.” The 1000 pieces of silver “covered the eyes” of the people with Sarah. The idiom and custom are difficult, but the essence is that the gift was to make it seem like no one saw what happened to Sarah, or if they saw what happened to her, they also saw that she was compensated for it, and thus she was vindicated or set right before all the people.