All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
This means that when the moon runs in its orbit, and it reaches the end of the orbit, it narrows, becomes smaller in size, bends like the crescent and becomes like the old date stalk. Al-Qurtubi, may Allaah have mercy in him, said: 'Qataadah said: 'The stalk is a dry bent bunch of a date-tree.' Al-Khaleel Ibn Ahmad said: 'The stalk is the root of the bunch, it is small and wide, and it resembles the crescent when it leans down.' Az-Zajaaj said: 'The stalk in the stick of the bunch from which stalks are cut, and it stays dry on the date tree. So, if the stalk is old, it withers and becomes like a crescent in its shape, so it becomes like the moon in its thinness, and yellowness. The meaning of "old" is the one on which a year or more elapses on it. When it is old, it becomes thin and curves down and becomes yellow in colour. It looks like the moon, because it has three similar traits: Thinness, curving, and yellowness.'
Allaah Knows best.