Sforno on Genesis 15:2/ספורנו על בראשית ט״ו:ב׳

1?מה תתן לי, a reference to the reward in this life.

2ערירי, “I have no son who can take my place.” Compare Jeremiah 22,30 כתבו את האיש הזה ערירי כי לא יצלח מזרעו איש יושב על כסא דוד, “record this man as without succession; one who shall never be found successful, for none of his offspring will be accepted to sit on the throne of David.” (the subject of this curse is כניהו son and heir of Yehoyakim)

3ובן משק ביתי הוא דמשק אליעזר, he is only a slave, known only in his home town. There can be no question but that similar actions performed by a slave who is in constant fear of his master’s disapproval, even if in fact the same as those performed by the master’s son, are different in quality, and in effect from one another. The same chores performed by the son are motivated by love instead of by fear.