What is the evidence that looking at a non-mahram woman with lust, while fearing temptation (fitna), is a major sin? And what is the ruling on that which leads to a major sin?

The basic principle regarding the forbidden gaze is that it is a minor sin, according to the hadith: "The fornication of the eyes is the gaze." Scholars have interpreted this as being among the "lamam" (minor transgressions) that Allah has forgiven.

However, looking at forbidden films can be considered a major sin due to the combination of lust and the fear of temptation involved, as well as the prevalence of addiction and persistence.

Generally, a minor sin transforms into a major one through persistence. The threshold of persistence that elevates a minor sin to a major one is repeated occurrence that indicates a lack of concern for religious matters. Indeed, persistent gazing with lust may be more corrupting than a single act of fornication without persistence. A major sin can sometimes be accompanied by factors that make it akin to a minor one, and a minor sin can be accompanied by factors that make it akin to a major one. This depends on the level of modesty, fear, and concern present in the heart.