Quotes from Engels, Dialectics of Nature (page numbers refer to MECW edtion, vol. 25)
Motion, interconnection

"The whole of nature accessible to us forms a system, an interconnected totality of bodies, and by bodies we understand here all material existences extending from stars to atoms.... In the fact that these bodies are interconnected is ready included that they react on one another, and it is precisely evident here that matter is unthinkable without motion. It already becomes evident herr that matter is unthinkable without motion." p. 363

"All motion consists of the interplay of attraction and repulsion."

"Dialectics has proved from the results of our experience of nature so far that all polar opposites in general are determined by the mutual action of the two opposite poles on each other, that the separation and opposition of these poles exist only within their mutual connection and union, and conversely, that their union exists only in their separation and their mutual connection only in their opposition." 364-365.