I've taken the time to go through the original series myself and list down various scenes and quotes that best illustrate the relationship that Haruka and Michiru have with each other. I've split them up into sections to make it a bit easier to browse.
Sailor Moon S
★ Episodes 92, 94 and 95
★ Episodes 98, 99, 101 and 103
★ Episode 106
★ Episodes 107, 110, 124 and 126
Sailor Moon SuperS
★ Special Episode 2 and SuperS Movie
Sailor Moon Sailor Stars
★ Episodes 167, 168 and 179
★ Episodes 180, 181, 184 and 194
★ Episodes 195, 196, 197, 198 and 200