Albert Barnes Commentary Exodus 21:6

"then his master shall bring him unto God, and shall bring him to the door, or unto the door-post; and his master shall bore his ear through with an awl; and he shall serve him for ever." — Exodus 21:6 (ASV)

Forever - That is, most probably, until the next Jubilee, when every Hebrew was set free. See Leviticus 25:40, Leviticus 25:50. The custom of boring the ear as a mark of slavery appears to have been a common one in ancient times, observed in many nations.

To the judges - Literally, “before the gods אלהים 'ĕlohı̂ym.” The word does not denote “judges” in a direct way, but it is to be understood as the name of God, in its ordinary plural form, God being the source of all justice. The name in this connection always has the definite article prefixed. See the marginal references. Compare Psalms 82:1, Psalms 82:6; John 10:34.