I have gained some hope from the Judge of Judgment Day, because you have placed some trust in what I said.

There is a delightful touch of playful wit here. The poet muses that if his chronically skeptical and hard-hearted beloved could finally show a glimmer of faith in his words, then surely the Ultimate Judge on the Day of Reckoning will be forgiving too. It charmingly implies that softening the beloved's heart was a far tougher trial than facing divine judgment.