A slave also; when it is not sufficient - עבד נמי בדלא ספיק
The מקשן assumed that (even if the master said צא מעשה ידיך במזונותיך) that he is obligated to feed his slave if the slave works for him (unless we maintain that the master can say עשה עמי ואיני זנך).
In order that people will see and have mercy - כי היכי דחזו אינשי ומרחמי
On one hand it is more apt to save someone from assimilation than to worry about his sustenance (רשב"ג); on the other hand one is more concerned for dying from hunger than a possible assimilation, especially since feeding is less expensive than redeeming (רבנן).
רב said one who sanctifies the hands of his slave - אמר רב המקדיש ידי עבדו
If one is מקדיש עבדו he becomes free and joins the עם קדוש; he does not become הקדש regarding his various actions, since the owner made only one general statement of הקדש and (in addition) he did not mention that he is מקדיש him for his work.