What has George told Lennie that he always remembers, even when Lennie forgets everything else?

Lennie is forgetful throughout the novella, and George is continually reminding him of recent events. In the first chapter, Lennie demonstrates his forgetful nature by not remembering that he and George are traveling to work at a ranch in Soledad, and he also forgets the incident in Weed. At the end of the first chapter, George tells Lennie to look around at their campsite beside the river and remember its appearance. George then tells Lennie that if anything ever happens, he needs to remember to follow the river and hide in the brush at the campsite. Later on in the novella, Lennie accidentally kills Curley's wife and remembers to run back to their original campsite by the river. At the beginning of chapter 6, Lennie says, "I di'n't forget, you bet, God damn. Hide in the brush an' wait for George" (Steinbeck, 58). George then meets up with Lennie and is forced to shoot his friend in order to save him from the brutal lynch mob.