Acts 16:31 New English Translation

³¹They replied,^[a] “Believe^[b] in the Lord Jesus^[c] and you will be saved, you and your household.”

Acts 16:31 tn Grk “said.”
Acts 16:31 sn Here the summary term of response is a call to believe. In this context it refers to trusting the sovereign God’s power to deliver, which events had just pictured for the jailer.
Acts 16:31 tc The majority of mss add Χριστόν (Christon, “Christ”) here (C D E Ψ 1739 M sy sa), but the best and earliest witnesses read simply τὸν κύριον ᾿Ιησοῦν (ton kurion Iēsoun, “the Lord Jesus”; P^74vid א A B 33 81 bo). The addition of “Christ” to “Lord Jesus” is an obviously motivated reading. Thus on both external and internal grounds, the shorter reading is strongly preferred.

New English Translation (NET)