The second is the completion of thirty days of Sha'ban, for a lunar month cannot exceed thirty days, nor can it be less than twenty-nine days. According to the madhhab, a third circumstance is added: that clouds or dust obstruct sighting it. This will be discussed later.

His statement, “If it is not seen on a clear night before the thirtieth, they are to begin the morning not fasting,” means: if the crescent is not seen on the night before the thirtieth day of Sha'ban when the sky is clear—free of clouds, dust, smoke, fog, and every other impediment to sighting—then they are to begin the morning not fasting, even if the crescent had in fact appeared. In this case, they must not fast, either because it is prohibited or because it is disliked, due to the Prophet’s saying: “Do not precede Ramadan by fasting one or two days before it, except for a man who habitually observes a fast; then let him observe it.” (1)

His statement, “But if clouds or dust obstruct it, then according to the apparent position of the madhhab, fasting is obligatory,” means: if clouds obstruct sighting the crescent—and clouds are cloud cover.

His statement, “or dust,” refers to the dust brought by the winds, as well as anything else that prevents it from being seen.