Binary stellar systems are unique astrophysical laboratories for the study of black holes (BHs). X-ray binaries and coalescing binary BHs have a lot of common threads. In fact, some types of high-mass X-ray binaries are considered as the potential immediate progenitors of Gravitational-Wave sources. The BH spin is one of the observable quantities in both types of systems, and it carries significant information about their past evolutionary history. In this talk, I will describe how, in the framework of the classical isolated binary formation channel, for both X-ray binaries and coalescing double compact objects, different phases of binary interactions are responsible for determining the observed spin in different types of BH binaries. The observed BH spins in low-mass X-ray binaries can be explained through accretion onto the BH after its formation. In contrast, the high spins of high-mass X-ray binaries can be explained when the BH progenitor star looses its envelope via a case-A mass-transfer and never expands to become a giant. Finally, I will show that the effective spin, as well as chirp masses and merger redshifts, of the currently observed LIGO BH mergers is fully consistent with the isolated binary formation channel, once one takes into account the appropriate physics of stellar rotation and angular momentum transport, the cosmological evolution of star-formation rate and metallicity, and the observational selection effects.