Tawbah - ,Dought & clear - , Is vowing part of repentance?

Do we have any chance of being forgiven if we do not vow to never
repeat the sin again.
I'm asking this because, if you think that you willmost probably do it
again, is there a point in vowing not to repeat the haram action
(knowing that to break a promise to Allah constitutes fasting for 3
days)?.
Praise be to Allaah.
No sin is too great for Allaah to forgive, no matter what this sin is,
so long as the person has repented from it. Allaah says
(interpretation of the meaning):
"Say: O 'Ibaadi (My slaves) who have transgressed against themselves
(by committing evil deeds and sins)! Despair not of the Mercy of
Allaah, verily, Allaah forgives all sins. Truly, He is Oft-Forgiving,
Most Merciful"
[al-Zumar 39:53]
The door of repentance is open so long as death has not come to a
person, and so long as the sun has not begun torise from the west.
It was narrated that Ibn 'Umar (may Allaah be pleased with him) said:
The Messenger of Allaah (peace and blessings of Allaah be upon him)
said: "Allaah accepts the repentance of His slave so long as the death
rattle has not yet reached his throat." Narrated by Ahmad, 2/132,
153); narrated and classed as hasan by al-Tirmidhi, 3537; also classed
as hasan by al-Albaani in Saheeh al-Targheeb, 3/318, 3413.
It was narrated that Abu Hurayrah (may Allaah be pleased with him)
said: The Messenger of Allaah (peace and blessings of Allaah be upon
him) said: "Whoever repents before the sun rises fromthe west, Allaah
will accept his repentance." Narrated by Muslim, 3073.
So the Muslim should make the most of this opportunity and this great
bounty from Allaah, and hasten to repent so long as there is still
time; he should not delay his repentance.
But this repentance has to be sincere, as Allaah says (interpretation
of the meaning):
"O you who believe! Turn to Allaah with sincere repentance! It may be
that your Lord will expiate from you your sins, and admit you into
Gardens under which rivers flow (Paradise) the Day that Allaah will
not disgrace the Prophet (Muhammad) and those who believe with him.
Their Light will run forward before them and (with their Records Books
of deeds) in their right hands. They will say: 'Our Lord! Keep perfect
our Light for us [and do not put it off till we cross over the Siraat
(a slippery bridge over Hell) safely] and grant usforgiveness. Verily,
You are Able to do all things'"
[al-Tahreem 66:8]
The scholars have stated that sincere repentance is that which meets
five conditions:
1- It should be sincerely for the sake of Allaah.
2- There should be real regret for sins committed in the past, and
the person should wish that he had never done them.
3- He should give up the sin immediately. If the sin consists of
doing something haraam, he should stop doing it at once. If the sin
consists of not doing something that is obligatory, he should start to
do it at once. If the sin has to do with people's dues, his repentance
is not valid unless he gives them those dues.
4- He should resolve never to go back to that sin in the future.
5- That should not come after the time when repentance is
accepted, as stated above.
See Majaalis Shahr Ramadaan by Ibn 'Uthaymeen, 143.
Hence we know that it isnot one of the conditions of repentance that
one should not repeat the sin, rather the condition is the sincere
resolve notto repeat it. If a person repents from a sin that he used
to commit, then the Shaytaan toys with him and makes him go back to it
- there is no power and no strength except with Allaah - he should not
despair of the mercy of Allaah. He should repent once again and Allaah
will accept it, for Allaah's bounty and forgiveness are immense.
It was narrated from AbuMoosa al-Ash'ari (may Allaah be pleased with
him) that the Prophet (peace and blessings of Allaah be upon him)
said: "Allaah spreads out His hand at night to accept the repentance
ofthose who committed sin during the day, and He spreads out His hand
during the day to accept the repentance of those who committed sin
during the night (and this will continue) until the sun rises from the
west."
Narrated by Muslim, 2759.
It was narrated from AbuHurayrah (may Allaah be pleased with him) that
he heard the Messenger of Allaah (peace and blessings of Allaah be
upon him) say: "A personcommitted a sin and said, 'O Lord, I have
sinned; forgive me.' His Lord said: 'Does My slave know that he has a
Lord Who forgives sin and punishes for it? I have forgiven My slave.'
Then as much time as Allaah willed passed, and he committed sin again.
He said, 'O Lord, I have sinned; forgive me.' His Lord said: 'Does My
slave know that he has a Lord Who forgives sin and punishes for it? I
have forgiven My slave.' ..."
Narrated by al-Bukhaari,7505; Muslim, 2753
But the wise Muslim should be sincere towards Allaah in his
repentance, and sincerely resolve not to repeat the sin, and regret
what he has donein the past. His repentance should not merely be words
that are spoken by his lips when the rest of his faculties pay no
heed; that is the repentance ofliars.
With regard to making vows not to commit this sin again, there is no
need for that. Sincere repentance is that whichfulfils the conditions
mentioned above.
It remains to comment on that which the questioner mentioned about the
one who breaks his vow having tofast for three days. This is not
always the case. Rather what the one who breaks his vow has to do is
to free a slave, or feed or clothe ten poor persons. If he cannot do
any of these things, then he has to fast for three days, but fasting
is only an option is he is unable to do any of the three other things,
as is indicated by the verse in which Allaahsays (interpretation of
the meaning):
"Allaah will not punish you for what is unintentional in your oaths,
but He will punishyou for your deliberate oaths; for its expiation
(adeliberate oath) feed ten Masaakeen (poor persons), on a scale of
the average of that with which you feed your own families, or clothe
them or manumit a slave. But whosoever cannot afford (that), then he
should fast for three days. That is the expiation for the oaths when
you have sworn. And protect your oaths (i.e. do not swear much).Thus
Allaah makes clear to you His Ayaat (proofs, evidences, verses,
lessons, signs, revelations, etc.) that you may be grateful"
[al-Maa'idah 5:89]
And Allaah knows best. May Allaah send blessings and peace upon our
Prophet Muhammad and his family and companions.