4:103
فَإِذَا قَضَيْتُمُ ٱلصَّلَوٰةَ فَٱذْكُرُوا۟ ٱللَّهَ قِيَٰمًۭا وَقُعُودًۭا وَعَلَىٰ جُنُوبِكُمْ ۚ فَإِذَا ٱطْمَأْنَنتُمْ فَأَقِيمُوا۟ ٱلصَّلَوٰةَ ۚ إِنَّ ٱلصَّلَوٰةَ كَانَتْ عَلَى ٱلْمُؤْمِنِينَ كِتَٰبًۭا مَّوْقُوتًۭا
And when you have completed the prayer, remember Allah standing, sitting, or [lying] on your sides. But when you become secure, re-establish [regular] prayer. Indeed, prayer has been decreed upon the believers a decree of specified times.
Translation · Saheeh International
Tafsir
Ibn Kathīr (abridged)
The Order for Ample Remembrance After the Fear Prayer
Allah commands Dhikr after finishing the Fear prayer, in particular, even though such Dhikr is encouraged after finishing other types of prayer in general. In the case of Fear prayer, Dhikr is encouraged even more because the pillars of the prayer are diminished since they move about while performing it, etc., unlike other prayers. Allah said about the Sacred Months,
فَلاَ تَظْلِمُواْ فِيهِنَّ أَنفُسَكُمْ
(so wrong not yourselves therein), even though injustice is prohibited all year long. However, injustice is particularly outlawed during the Sacred Months due to their sanctity and honor. So Allah's statement,
فَإِذَا قَضَيْتُمُ الصَّلَوةَ فَاذْكُرُواْ اللَّهَ قِيَـماً وَقُعُوداً وَعَلَى جُنُوبِكُمْ
(When you have finished Salah, remember Allah standing, sitting down, and on your sides,) means, in all conditions,