Radak on Genesis
ויאמר עבד אברהם אנכי, our sages (Baba Kama 92) consider this as an example of a popular proverb that one should mention any personal deficiency before commencing to carry out whatever mission has been assigned to him. [according to this interpretation Eliezer, instead of considering it a privilege to be the servant of a man like Avraham, considered it a stigma that he was a slave. Ed.]
Rav Hirsch on Torah
Ihr habts richtig herausgefühlt, bin nicht der Herr, bin nur der Knecht.