Musar על בבא קמא 51:25

חטאתי כי לא ידעתי . At first glance it seems strange that if Bileam was not aware of the angel's presence, (which had impeded the she-ass's progress), how he could have sinned. Man is responsible for ignorance of certain laws however, if they were the ones he should have known. Otherwise there would be no point in G–d equipping us with a brain. Bileam's mental faculties were such that he should have seen the angel. If even his ass could see the angel, his own lack of awareness could only be due to a sinful outlook on his part. Man is duty-bound to always be on guard not to be the cause of something sinful.

It teaches us that intellectually alert people who conduct themselves with the proper degree of discretion and caution will assure themselves of the blessing in Daniel 12,3: "The wise will shine like the radiance of the firmament, and those who make the many righteous, like the stars, forever and ever."

When an ox gores man, the Torah says: סקול יסקל, etc." (21,28). The Torah distinguishes between a שור תם, an ox that has a history of behaving peacefully, and one that has demonstrated aggressiveness. If the normally tame ox has killed a human being, it immediately is categorised as an aggressive beast, the owner being considered as having been forewarned. I have explained these distinctions at length in my commentary on פרשת וישב, in connection with the festival of חנוכה.
אדם הראשון, first man, was considered מועד לעולם, forewarned from the outset (Baba Kama 3). This means that he was unable to make excuses for his sin, having been told by G–d directly what he must not do. יעקב on the other hand, is described as איש תם (the choicest of human beings), and only had to pay half for any sins he had committed (i.e. cost of any damage he caused), since he never died (cf. Taanit 5, that יעקב אבינו לא מת). This means that though he "died," he did not die completely as was explained in that context (see Akeydat Yitzchak chapter 32).