«وتناسب الفعليتين في المضي والمضارعة»
Correspondence between two verbal clauses in their past or imperfect forms.
When the intended viewpoint is parallel, past with past or imperfect with imperfect may be stylistically elegant. A deliberate tense difference, however, can be meaningful when one act is completed and another ongoing.
The aim is not mechanical tense matching. It is to express the intended temporal relationship with accuracy and rhetorical fitness.