Allah, the Exalted, says: “And remember your Rubb by your tongue and within yourself, humbly and with fear and without loudness in words in the mornings, and in the afternoons and be not of those who are neglectful.” (7:205)
“And declare the perfectness of your Rubb before the rising of the sun, and before its setting.” (20:130)
“And declare the perfectness of your Rubb and praise Him in the Ashi (i.e., the time period after midday till sunset) and in the Ibkar (i.e., the time period from early morning or sunrise till before midnoon).” (40:55)
“In houses (mosques) which Allah has ordered to be raised (to be cleaned, and to be honored), in them His Name is mentioned in the mornings and the afternoons or the evenings. Men whom neither trade nor sale diverts from the remembrance of Allah (with heart and tongue).” (24:36,37)
“Verily, We made the mountains to declare the Perfectness of Allah with him [Dawud (David)] in the `Ashi (i.e., after the midday till sunset) and Ishraq (i.e., after the sunrise till midday).” (38:18)
Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said, “He who recites in the morning and in the evening the statement: `Subhan-Allahi wa bihamdihi (Allah is free from imperfection and I begin with praising Him)’ one hundred times, will not be surpassed on the Day of Resurrection by anyone with better deeds than one who utters the same words or utters more of these words.” [Muslim].
Shahr bin Haushab reported: I asked Umm Salamah (May Allah be pleased with her), “O Mother of the Believers! Which supplication did the Messenger of Allah (PBUH) make frequently when he was in your house?” She said: “He (PBUH) supplicated frequently: Ya muqallib (O Controller of the hearts, make my heart steadfast in Your religion).” [At-Tirmidhi].
Commentary: Steadfastness in religion is the conduct of great men, which cannot be acquired without the special Grace of Allah. Many turns occur in a person’s life when he becomes slack or negligent in religious matters or when he deviates from the course prescribed by religion. This prayer has outstanding importance for people who are faced with such a situation. They should recite this prayer very frequently. In fact, they should make its recitation a permanent feature.
Anas (May Allah be pleased with him) reported: The supplication most often recited by the Prophet (PBUH)
was: “Allahumma atina fid-dunya hasanatan, wa fil-akhirati hasanatan, wa qina `adhab-annar (O our Rubb! give us in this world that which is good and in the Hereafter that which is good, and save us from the punishment of the Fire).” [Al-Bukhari and Muslim].
In the narration of Muslim, it is added that whenever Anas supplicated, he used to beseech Allah with this Dua.
Commentary: It is desirable to recite this Dua which is mentioned in the Qur’an (2:201) and which comprehends all that is good, both in this life and the Hereafter. The Prophet (PBUH) made it a habit to recite this Dua, and the Companions were eager to follow him in all his words and actions.
source : Book of Riyadus-Saliheen