Is Christ thy advocate to plead thy cause?
Art thou his client? Such shall never slide.
He never lost his case.

The lines cast salvation in legal terms: Christ is imagined as an advocate who pleads a believer’s case before divine judgment, while the sinner is the “client.” The speaker presses the reader toward self-examination—are you truly under Christ’s representation? If so, the promise follows: such a person “shall never slide,” i.e., will not finally fall away or be lost. “He never lost his case” underscores Christ’s perfect efficacy as mediator: his intercession is unfailing, not merely persuasive. The rhetoric blends pastoral assurance with a warning that the benefit applies only to those genuinely joined to Christ.