«وقد يكون الفاء لبيان العلة»
Faa may also introduce an explanatory cause.
In a construction like “أبشر فقد أتاك الغوث,” the arrival of assistance explains why the speaker gives good news. It does not imply that giving the good news first caused the help to arrive.
To interpret such a construction, first identify the statement and its supporting reason. Then decide whether faa reports a later event in sequence or introduces the reason that justifies what was said.