Who is the trustworthy one whose sighting is sufficient to prove the month of Ramadan?

Justice, linguistically: uprightness. Legally: one who fulfills obligations, does not commit a major sin, and does not persist in a minor one, such as performing the five daily prayers and avoiding backbiting and slander. For justice, strong eyesight is a prerequisite; a person with poor eyesight, even if just, has their testimony rejected because they are prone to error. The evidence for this is that Allah Almighty made strength and trustworthiness conditions for assigning work, as in the story of Musa with the daughter of the man of Midian: ﴿O my father, hire him. Indeed, the best of those you could hire is the strong, the trustworthy.﴾ And the saying of the 'ifrit: ﴿And indeed, I am powerful and trustworthy over it.﴾ These two attributes are fundamental to every task, including giving testimony.