Let us say for the purposes of this scenario that the Byzantine Emperor Maurice opts to forgo his Balkan Campaign, at least temporarily, rather than wintering the troops north of the Danube due to budget problems, leading to the cascade of mutiny eventually leading to the army's declaration in favor of Phocas.
How does Maurice's continued occupation of the Eastern Roman throne affect the Empire's near-term prospects, both internally and externally? It's unlikely that a near-future war with the Sassanids would occur, at least one in the manner of the disastrous 602-628 conflict, meaning that the two powers probably remain at an impasse for the time being. Presuming that a war similar in magnitude and effect doesn't happen anytime soon, this leads to the Sasanian Empire most likely not succumbing to bankruptcy and political instability as it did postwar.
Moreover, there is the possibility that Muhammad's founding of Islam is not butterflied, which if it manages to spread in a manner similar to OTL would lead to the first caliphate (and with it a mostly-unified Arabia) facing a pair of healthy empires rather than one bankrupt and one collapsing one, most likely either hemming in expansionist ambitions for the time being or diverting them to another direction. How might the corralling of the early Caliphate (if it came to existence) impact the development of Islamic belief/doctrine and impact its spread?