Winter was considered the spring of the believer because the gardens of worship are enjoyed during it, the grounds of worship are roamed freely in it, and the hearts enjoy the ease of worship that is facilitated in its gardens.
As for the lengthening of the night in winter, then it is so long that a person can take his need from sleep then get up for the night prayer. So the person can recite all he planned from the Quran while getting enough sleep. So the needed rest and reciting his planned portion from the Quran are combined; he/she attains the religious benefits in addition to giving the body the needed rest.
و أما قيام ليل الشتاء فلطوله يمكن أن تأخذ النفس حظها من النوم ثم تقوم بعد ذلك إلى الصلاة فيقرأ المصلي ورده كله من القرآن و قد أخذت نفسه حظها من النوم فيجتمع له فيه نومه المحتاج إليه مع إدراك ورده من القرآن فيكمل له مصلحة دينه و راحة بدنه