Bukhari
Volume 1, Book 2, Number 37:
Narrated Abu Huraira:

Allah's Apostle said, "Whoever observes fasts during the month of Ramadan out of sincere faith, and hoping to attain Allah's rewards, then all his past sins will be forgiven."

Bukhari
Volume 1, Book 2, Number 36:
Narrated Abu Huraira:

Allah's Apostle said: "Whoever establishes prayers during the nights of Ramadan faithfully out of sincere faith and hoping to attain Allah's rewards (not for showing off), all his past sins will be forgiven."

Narrated by Anas bin Malik (Radhiallaho anho):
The Prophet (sallallaahu 'alaihi wasallam) said, "Take Suhur as
there is a blessing in it."

Bukhari Vol. 3 : No. 146

Narrated by Abu Huraira (Radhiallaho anho):
Allah's Messenger (sallallaahu 'alaihi wasallam) said, "Allah
said, 'All the deeds of Adam's sons (people) are for them,
except fasting which is for Me, and I will give the reward for
it.' Fasting is a shield or protection from the fire and from
committing sins. If one of you is fasting, he should avoid
sexual relation with his wife and quarreling, and if somebody
should fight or quarrel with him, he should say, 'I am fasting.'
By Him in Whose Hands my soul is, the unpleasant smell coming
out from the mouth of a fasting person is better in the sight
of Allah than the smell of musk. There are two pleasures for
the fasting person, one at the time of breaking his fast, and
the other at the time when he will meet his Lord; then he will
be pleased because of his fasting."

Bukhari Vol. 3 : No. 128

Narrated by Abu Huraira (Radhiallaho anho):
The Prophet (sallallaahu 'alaihi wasallam) said, "Whoever does
not give up forged speech and evil actions, Allah is not in
need of his leaving his food and drink (i.e. Allah will not
accept his fasting.)"

Bukhari Vol. 3 : No. 127

Narrated by Abu Huraira (Radhiallaho anho):
Allah's Messenger (sallallaahu 'alaihi wasallam) said, "When
the month of Ramadan starts, the gates of the heaven are opened
and the gates of Hell are closed and the devils are chained."

Bukhari Vol. 3 : No. 123

Sufyan bin `Abdullah (May Allah be pleased with him) reported: I said, "O Messenger of Allah, tell me something of Islam which I will not ask anyone else about it.'' He (PBUH) said, "Say, `I believe in Allah' and then be steadfast".
[Muslim].

Commentary: Steadfastness means adhering firmly to the injunctions of Islam, to act upon what is ordained and avoid what is prohibited, to perform dutifully orders in respect of obligations and what is regarded desirable and avoid what is unlawful. Faith is not a mere expression of Shahadah. The real Faith is one which is coupled with its actual practice because practice of religion is in fact the fruit of Faith. A tree which does not bear any fruit, has no value, similarly; faith becomes meaningless without practice. Steadfastness is the mark of perfect Faith.