The foundation of the show where Ishita saves Ruhi from an accident, leading to her first (often tense) encounters with Raman. The Marriage for Ruhi (Ep. 60-70):
If you are looking for the most impactful and highly-rated moments, these episodes are considered the series' best: Yeh Hai Mohabbatein - JioHotstar yeh hai mohabbatein all episodes best