﴿وَذكر الله كثيرا﴾ [And remember Allah much]. This refers to the voluntary remembrance, for which there is no specified time.
﴿وَذكر الله كثيرا﴾ وَهَذَا ذِكْرُ التَّطَوُّعِ لَيْسَ فِيهِ وَقت.