In winter, the nights are long and the days are short. This is a great blessing from Allāh ta‘ālā which we should take full benefit from. Due to the long nights, one can have a good night’s sleep and still have the opportunity of performing Tahajjud Ṣalāh. And as the days are short and the heat less, fasting also becomes relatively easy. Therefore, in winter, one should try to perform Tahajjud and also fast, especially the residents of countries which are cold in climate. Sayyidunā ‘Abdullāh Ibn ‘Umar radiyallāhu ‘anhu would say upon the commencement of winter:
The night has become long for your Tahajjud Ṣalāh and the day has become short for your fast, so take full benefit from this.
Those who have qaḍā (missed) fasts should value these days and absolve themselves from their obligation. And those who do not have any qaḍā fasts should try to fast the way Sayyidunā Dāwūd ‘alayhis-salām used to fast; fasting a day and leaving the next. Our beloved Nabī sallallāhu ‘alayhi wasallam states:
The most beloved fasts in the sight of Allāh are the fasts of Dāwūd. He used to fast a day and leave a day. (Al-Bukhārī)
If this is not in one’s capability, then at the least, one should endeavour to fast on Monday and Thursday, and on the Ayyāmul-Bīd (the 13th, 14th and 15th of every Islamic Month).
May Allāh ta‘ālā grant us the ability to act upon these points. Āmīn.