Allah says:

[فَادْعُواْ اللَّهَ مُخْلِصِينَ لَهُ الدِّينَ وَلَوْ كَرِهَ الْكَـفِرُونَ ]

(So, call you upon Allah making religion sincerely for Him, however much the disbelievers may hate.) This means, worship Allah and call upon Him alone in all sincerity. Do not be like the idolators in conduct and beliefs. Imam Ahmad recorded that after ending every prayer, `Abdullah bin Az-Zubayr used to say: "There is no (true) God except Allah Alone with no partner or associate, His is the dominion and praise, for He is able to do all things; there is no strength and no power except with Allah; there is no (true) God except Allah and we worship none but Him; to Him belongs the blessings and the virtue and good praise; there is no (true) God except Allah, we worship Him in all sincerity even though the disbelievers may hate that.'' He said, "The Messenger of Allah used to say Tahlil with this after every prayer.'' Something similar was also recorded by Muslim, Abu Dawud and An-Nasa'i. It was reported in Sahih from Ibn Az-Zubayr, may Allah be pleased with him, that the Messenger of Allah used to say the following after the prescribed (obligatory) prayers:

«لَا إِلهَ إِلَّا اللهُ وَحْدَهُ لَا شَرِيكَ لَهُ، لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ، وَهُوَ عَلى كُلِّ شَيْءٍ قَدِيرٌ، لَا حَوْلَ وَلَا قُوَّةَ إِلَّا بِاللهِ، لَا إِلهَ إِلَّا اللهُ، وَلَا نَعْبُدُ إِلَّا إِيَّاهُ، لَهُ النِّعْمَةُ وَلَهُ الْفَضْلُ وَلَهُ الثَّــنَاءُ الْحَسَنُ، لَا إِلهَ إِلَّا اللهُ مُخْلِصِينَ لَهُ الدِّينَ وَلَوْ كَرِهَ الْكَافِرُون»

(There is no (true) God except Allah Alone with no partner or associate, His is the dominion and praise, for He is able to do all things; there is no strength and no power except with Allah; there is no (true) God except Allah and we worship none but Him; His is the blessing and virtue and good praise; there is no (true) God except Allah, we worship Him in all sincerity even though the disbelievers hate that.)

[رَفِيعُ الدَّرَجَـتِ ذُو الْعَرْشِ يُلْقِى الرُّوحَ مِنْ أَمْرِهِ عَلَى مَن يَشَآءُ مِنْ عِبَادِهِ لِيُنذِرَ يَوْمَ التَّلاَقِ - يَوْمَ هُم بَـرِزُونَ لاَ يَخْفَى عَلَى اللَّهِ مِنْهُمْ شَىْءٌ لِّمَنِ الْمُلْكُ الْيَوْمَ لِلَّهِ الْوَحِدِ الْقَهَّارِ - الْيَوْمَ تُجْزَى كُلُّ نَفْسٍ بِمَا كَـسَبَتْ لاَ ظُلْمَ الْيَوْمَ إِنَّ اللَّهَ سَرِيعُ الْحِسَابِ ]

(15. (He is Allah) Owner of high ranks and degrees, the Owner of the Throne. He sends the revelation by His command to any of His servants He wills, that he may warn of the Day of Mutual Meeting.) (16. The Day when they will come out, nothing of them will be hidden from Allah. Whose is the kingdom this Day It is Allah's, the One, the Irresistible!) (17. This Day shall every person be recompensed for what he earned. This Day no injustice. Truly, Allah is swift in reckoning.)