συνεθιστέον
From LSJ
Ὅρκον δὲ φεῦγε καὶ δικαίως κἀδίκως (κἂν δικαίως ὀμνύῃς) → Iurare fugias, vere, falso, haud interest → Zu schwören meide, gleich ob richtig oder falsch
English (LSJ)
A one must accustom oneself, c. inf., Pl.R.520c. II one must accustom, πρὸς ταῦτα σ. αὑτούς, folld. by infs., Plu.2.522d.