I have told you this is the same expression used in 15.11 and 14.25 (see there). The immediate reference is to 15.18-27.

Give up your faith translates the same verb used in 6.61 (see there); it occurs in John’s gospel only in these two verses, and in both it is a very strong term. So that you will not give up your faith is translated by Jerusalem Bible “so that your faith may not be shaken” (New American Bible “to keep your faith from being shaken”), and by New English Bible “to guard you against the breakdown of your faith.” The focus of Good News Translation and New English Bible is closer to the meaning of the Greek text; the reference is to giving up or falling away from one’s faith. It is not merely a matter of having one’s faith shaken. In a number of languages “giving up faith” is essentially equivalent to “ceasing to believe,” “stop trusting,” or “cease putting one’s confidence in.”

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .