He used to miss some prayers – does he have to renew the marriage contract?

Firstly: 

The difference of opinion among the scholars concerning the
ruling on one who does not pray out of laziness is justifiable. But what is
indicated by the sound evidence is that he is a kaafir. For more information
on the evidence please see question no. 5208. 

Secondly: 

If the one who does not pray repents and prays, then he has
come back to Islam and he does not need to repeat the Shahaadatayn. 

Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him)
said: As for the one who does not pray sometimes and does not make them up
and does not intend to make them up, or he misses some of the obligatory
parts of the prayer and does not make them up or intend to make them up,
many of our companions ruled that he becomes a kaafir thereby… Then when he
prays again he becomes a believer, as is indicated by the words of the
Prophet (peace and blessings of Allaah be upon him): “Whoever misses
‘Asr prayer deliberately, his good deeds will be lost.” And he (peace
and blessings of Allaah be upon him) said: “Whoever misses a prayer
deliberately is no longer under the protection of Allaah.” End quote. 

He also said: If he prays after stopping praying, he comes
back to Islam from apostasy, and his prayer is valid, unlike the one who was
originally a kaafir, whose prayer is not valid until after he says the
Shahaadatayn, because the kufr of the former is due to failing to do
something, and if he does it he comes back to Islam. In the case where a
person’s kufr results from rejecting (some of the obligations of Islam), if
he then accepts and affirms the obligation, then he rejoins Islam. 

If it is said that in cases other than this, the apostate’s
return to Islam is not valid unless he utters the Shahaadatayn, no matter
what form his apostasy took, the answer is that it is because he denied
something, so he must speak words of affirmation, starting with the
Shahaadatayn, which implies accepting everything else. But in this case (the
one who does not pray), he accepts that it is obligatory, so all he needs to
do is to do it in order to rejoin Islam. End quote. 

Based on this, your saying “thus I am still a kaafir and
Allaah will not accept any deed from me” is incorrect, rather your having
repented to Allaah and your performing the prayers mean that you are no
longer a kaafir, and the one who repents from sin is like one who did not
sin at all. 

Thirdly: 

You do not have to renew your marriage contract, unless it
was done when one or both of you was not praying, in which case you have to
renew it. 

But if the prayers were missed after you got married, you do
not have to renew the marriage contract, because if one of the spouses
apostatizes then returns to Islam during the ‘iddah period, then the
original marriage contract is still valid and they do not need to repeat the
contract. Some scholars are even of the view that the original contract is
still valid even if he comes back to Islam after the end of the ‘iddah, so
long as they both agree to come back. This is the correct view. For more
information on that please see question no.
21690. 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was
asked: What is the ruling on a married woman staying with a husband who does
not pray and he has children from her? 

He replied: 

If a woman is married to a man who does not pray in
congregation or at home, then the marriage is not valid, because the one who
does not pray is a kaafir, as is indicated by the Holy Qur’aan and the
Sunnah and the views of the Sahaabah. ‘Abd-Allaah ibn Shaqeeq said: The
companions of the Prophet (peace and blessings of Allaah be upon him)
did not regard the omission of any deed to be kufr except prayer. 

It is not permissible for a kaafir to marry a Muslim woman
because Allaah says (interpretation of the meaning): 

“then if you ascertain that they are true believers send
them not back to the disbelievers. They are not lawful (wives) for the
disbelievers nor are the disbelievers lawful (husbands) for them”

[al-Mumtahanah 60:10]

If he stops praying after getting married, then the marriage
contract is annulled, unless he repents and comes back to Islam. Some of the
scholars limited that to the end of the ‘iddah; once the ‘iddah ends then it
is not permissible for him to go back to her if he becomes Muslim, except
with a new marriage contract.  

The woman has to separate from him and not allow him to be
intimate with her unless he repents and starts to pray, even if she has
children from him, because in this case the father does not have custody of
the children.” End quote from Fataawa Arkaan al-Islam, p. 279. 

This applies if he has stopped praying altogether. But if he
misses some of the prayers, then some of the scholars do not regard him as
having become a kaafir thereby. This is the view of Shaykh al-Islam Ibn
Taymiyah and Ibn ‘Uthaymeen (may Allaah have mercy on him). And some of the
scholars say that the one who misses a single obligatory prayer deliberately
until the time for it and the time for a prayer to which it may be joined is
over, becomes a kaafir thereby, such as if he delays Zuhr until the sun
sets. But if this person who has missed an obligatory prayer starts to pray
again before the ‘iddah is over, he comes back to Islam and his marriage
continues. 

Your question does not suggest that either of you stopped
praying for a long time that would include the ‘iddah period, rather at the
most you did not pray sometimes, then you went back to praying. This means
that the marriage contract is still valid, as stated above. 

It seems to us from your question that you do not have to
renew the marriage contract. 

Firstly, because when you did not pray, you did not stop
praying altogether, rather you missed some prayers, and this does not
constitute kufr according to many scholars, unless one stops praying
altogether. 

Secondly: This missing some prayers – even if we assume that
it is kufr – was for a short time during which the ‘iddah could not have
ended, and going back to prayer before the ‘iddah ends does not invalidate
the marriage contract and it remains valid as it was before missing
prayers. 

Fourthly: 

If a person stops praying then repents from that, he does not
have to make up the prayers that he missed, according to the more correct
view, but he should do a lot of naafil acts of worship and good deeds,
because Allaah says (interpretation of the meaning): 

“And verily, I am indeed forgiving to him who repents,
believes (in My Oneness, and associates none in worship with Me) and does
righteous good deeds, and then remains constant in doing them (till his
death)”

[Ta-Ha 20:82]

For more information on that, please see the answer to
question no. 91411. 

We ask Allaah to guide us and you. 

And Allaah knows best.