He who forgets the prayer should say it when he remembers it, there is no explation for it, except this. Qatada said: (Allah says)" And observe prayer for remembrance of Me"
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَنْ نَسِيَ صَلاَةً فَلْيُصَلِّهَا إِذَا ذَكَرَهَا لاَ كَفَّارَةَ لَهَا إِلاَّ ذَلِكَ قَالَ قَتَادَةُ وَأَقِمِ الصَّلاَةَ لِذِكْرِي