allah the all-mighty has said:
"فَاذْكُرُونِي أَذْكُرْكُمْ وَاشْكُرُوا لِي وَلَا تَكْفُرُونِ". البقرة 152
"therefore remember me. i will remember you. be grateful to me and never show me ingratitude" - al-baqarah 2:152
and he said:
"يَا أَيُّهَا الَّذِينَ آمَنُوا اذْكُرُوا اللهَ ذِكْرًا كَثِيراً". الأحزاب 41
"o you who believe, remember allah with much rememberance." - al-ahzab 33:41
and he said:
"وَالذَّاكِرِينَ اللهَ كَثِيرًا وَالذَّاكِرَاتِ أَعَدَّ اللهُ لَهُمْ مَغْفِرَةً وَأَجْرًا عَظِيمًا". الأحزاب 35
"and the men and women who remember allah frequently, allah has prepared for them forgiveness and great reward." - al-ahzab 33:35
and he said:
"وَاذْكُرْ رَبَّكَ فِي نَفْسِكَ تَضَرُّعًا وَخِيفَةً وَدُونَ الْجَهْرِ مِنَ الْقَوْلِ بِالْغُدُوِّ وَالْآصَالِ وَلَا تَكُنْ مِنَ الْغَافِلِينَ". الأعراف 205
"and remember your lord by your tongue and within yourself, humbly and in awe, without loudness, by words in the morning and in the afternoon, and be not among those who are neglectful." - al-araf 7:205
the prophet (pbuh) said: "he who remembers his lord and he who does not remember his lord are like the living and the dead." - al-bukhari, cf., al-asqalani, fathul-bari 11/208; muslim 1/539 with the wording "the house in which allah is remembered and the house in which allah is not remembered is like the living and the dead."
and he said, "shall i not inform you of the best of your works, the purest of them with your master (allah), the loftiest of them in your stations, the thing that is better for you than spending gold and silver (in charity), and better for you than meeting your enemies and slaying them and being slain by them?" they (the companions) said, "of course!" he said, "rememberance of allah, the most high." - at-tirmithi 5/459, ibn majah 2/1245. see al-albani, sahih ibn majah 2/316 and sahih at-tirmithi 3/139.
and he said, "allah the most high says, 'i amd with my slave when he thinks of me and i am with him when he mentions me. for if he mentions me to himself, i mention him to myself; and if he mentions me in a gathering, i mention him in superior gathering. if he approaches me by a hand's width, i approach him by an arm's length, i approach him by two arms length. and if he comes to me walking, i hasten to him swiftly.'" - al-ukhari 8/171, muslim 4/2061; this wording is from al-bukhari.
abdullah bin busr (raa) said that a man asked the prophet (pbuh), "o messenger of allah! verily, the sanctions of islam have become too numerous for me (to perform them all). inform me of something (simple) that i may adhere to." the prophet (pbuh) said, "let your tongue always be moist with the rememberance of allah." - at-0tirmithi 5/458, ibn majah 2/1246. see al-albani, sahih at-tirmithi 3/139 and sahih ibn majah 2/317.
and he said, "whoever reads one letter from the book of allah, will receive one hasanah (reward for a good deed), and one hasanah comes with ten like it. i do not say that alif-lam-mim is a letter. indeed alif is a letter, and lam is a letter, and mim is a letter." - at-tirmithi 5/175. see al-albani, sahih at-tirmithi 3/9 and sahihul-jami' as-saghir 5/340.
uqbah bin amir (raa) said: the messenger of allah (pbuh) came out (from his house) and we were of the porch (as-suffah). so he said, "who of you would like to go out in the morning everyday to the valley of buthan or al-'aqeeq and come back with two large she camels without commiting any sin or severing any family ties?" we replied, "o messenger of allah! all of us would like this." so he said, "would one of you not go to the masjid and learn to recite two verses from the book of allah, the mighty and majestic? that would be better than two she camels. and three verses would be better for him than three she-camels. and four verses would be better than four she-camels, and whatever their number may be of camels." - muslim 1/553
and he said, "whoever sits and does not mention the name of allah (before he rises) will find it a cause of sorrowfrom allah. whoever lies down to sleep and does npt mention the name of allah before rising, will find it a cause of sorrow from allah." - abu dawud 4/264. see al-albani, sahihul-jami' as-saghir 5/342.
and the prophet (saw) said: "no people sit in an assembly without mentioning allah, and without asking allah for blessings on their prophet, except that it will be a cause of sorrow upon them. thus if he (allah) wishes he will punish them, and if he wishes he will forgive them." - at-tirmithi. see al-albani, sahih at-tirmithi 3/140.
and he said: "no people may rise from an assembly in which they have failed to mention the name of allah without it being as if they were getting off a dead donkeys rotting back, and it would be a cause of grief for them." - abu dawud 4/264, ahmad 2/389. see al-albani, sahihul-jami' 5/176.