<p>The rapid expansion of cloud services and the proliferation of Internet of Things (IoT) devices have prompted a shift towards utilizing edge computing to enhance service delivery and reduce latency. This systematic review explores the concept of voluntary resource sharing at the network edge as a means to provide cloud services. Specifically, we focus on passive resource sharing strategies for executing cloud services at the network edge. By examining 54 scholarly articles published between 2018 and October 2024, we present a comprehensive taxonomy of their findings. This review highlights key strategies, frameworks, and technologies employed in voluntary edge resource sharing, including incentive mechanisms and resource allocation strategies. Additionally, we identify challenges and opportunities associated with this paradigm, such as scalability, security, and resource management. The findings aim to provide a thorough understanding of current advancements and future directions in edge resource sharing, offering valuable insights for researchers and practitioners in the field of distributed computing.</p>