أعدى الزمان سخاؤه فسخا به
His generosity spread to time itself, so that time became generous with him.
ولقد يكون به الزمان بخيلا
Yet time may also be miserly with respect to him.
Abū al-Ṭayyib presents two imagined states of time: it becomes generous through the patron's influence, yet can be described as miserly in relation to that same patron.
The new construction is related to the older image of time's miserliness but expands it into a more complex rhetorical argument.