Indeed, We know that your breast becomes tight because of what they say. So glorify the praises of your Lord and be of those who prostrate themselves (to Him).
meaning `We know, O Muhammad, that you are distressed by their insults towards you, but do not let that weaken your resolve or cause you to give up conveying the Message of Allah. Put your trust in Him, for He will suffice you and will support you against them. Keep yourself busy with remembering Allah, praising Him, glorifying Him, and worshipping Him (which means Salah, or prayer)'
Hence Allah says;
فَسَبِّحْ بِحَمْدِ رَبِّكَ وَكُن مِّنَ السَّاجِدِينَ
(So glorify the praises of your Lord and be of those who prostrate themselves (to Him).
Imam Ahmad reported from Nu`aym bin Hammar that he heard the Messenger of Allah say;
قَالَ اللهُ تَعَالَى
يَا ابْنَ ادَمَ لَاا تَعْجَزْ عَنْ أَرْبَعِ رَكَعَاتٍ مِنْ أَوَّلِ النَّهَارِ أَكْفِكَ اخِرَه
"O son of Adam! It is not too difficult for you to perform four Rak`ah at the beginning of the day, (and if you do them,) I will take care of you until the end of it."
وَاعْبُدْ رَبَّكَ حَتَّى يَأْتِيَكَ الْيَقِينُ