John Gill Commentary 1 Peter 2:18

"Servants, [be] in subjection to your masters with all fear; not only to the good and gentle, but also to the froward." — 1 Peter 2:18 (ASV)

Servants, be subject to your masters
This was another notion of the Jews, that because they were the seed of Abraham, they ought not to be the servants of any; and particularly such as were believers in Christ thought they ought not to serve unbelieving masters, nor indeed believing ones, because they were equally brethren in Christ with them; hence the Apostle Peter, here, as the Apostle Paul frequently elsewhere, inculcates this duty of servants to their masters; see (1 Corinthians 7:20 1 Corinthians 7:21) (Ephesians 6:5) (Colossians 3:22) (1 Timothy 6:1) (2 Timothy 2:9) the manner in which they are to be subject to them is,

with all fear ;
with reverence to their persons, strict regard to their commands, faithfulness in any trust reposed in them, diligence in the discharge of their duty, and carefulness of offending them: and all this,

not only to the good and gentle ;
those that are good natured, kind, beneficent, and merciful; that do not use them with rigour and severity; are moderate in their demands of service; require no more to be done than what is reasonable; allow them sufficient diet, give them good wages, and pay them duly:

but also to the froward ;
the ill natured, morose, and rigorous; who exact more labour than is requisite; give hard words, and harder blows; withhold sufficiency of food from them, and keep back the hire of their labours.