Ikrimah (may Allah have mercy on him) said: Umar bin Abd al-Aziz (may Allah have mercy on him) sent word to me (saying): I have sworn that I will not do such-and-such for a hin; so what is meant by the hin that cannot be determined? He recited: "Has there come upon man a period (hin) of time" [Surah al-Insan: 1] — no one knows how much time has passed since Allah created him. But as for the word hin that is in this saying of Allah: "It brings forth its fruit every hin" [Surah Ibrahim: 25], it means the interval between the fruit appearing and the fruit being picked.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 20020