He loves his deceased father and wants to do something good for him
Question

I am submitting this question of mine to you as I am worried about my father (may Allah have mercy on him). My father died two years ago, and he had some shortcomings in his duty towards the Lord of the Worlds, as follows:

He did not offer the prescribed prayers regularly. Sometimes he would pray, and sometimes he would not do so because of laziness, although he did not deny that it is obligatory.
He rarely fasted in Ramadan, on the grounds that he was sick and had to take heart medicine, or that he was weak and unable to fast, but he used to smoke, and I think that he did not fast regularly because he found it too difficult to give up smoking.
A long time ago, we had a grocery store, and as far as I know and as far as I remember, he did not give zakaah on the goods in the store. We were not well-off at all, and our business was not successful, and we sold the store after that.
Sometimes he had enough money that he could have done Hajj, but he did not do Hajj. He always told me that he wished he could go for Hajj, but he was not able to do so, because he suffered from a lot of serious problems in his eyes, and he had to avoid crowds and keep out of the sun and avoid exhaustion. But after he died, some people volunteered to do Hajj on his behalf – I think three different people did that, and they were not his relatives.

I loved my father a great deal, and everyone who knew him loved him. Hence I hope that you can explain to me what I can do to honour my father. I love him and fear for him the punishment of the grave and the punishment of the Day of Resurrection.
Praise be to Allah.If you want to benefit your father and honour him after his death, then you can benefit him in the following ways:

Offering sincere supplication (du‘aa’) for him.

Allah, may He be exalted, tells us that Ibraaheem (peace be upon him) said (interpretation of the meaning):
“My Lord, make me an establisher of prayer, and [many] from my descendants. Our Lord, and accept my supplication.
Our Lord, forgive me and my parents and the believers the Day the account is established”
[Ibraaheem 14:40-41].
It was narrated that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (sa) (blessings and peace of Allah be upon him) said: “When a man dies, all his good deeds come to an end except three: ongoing charity (sadaqah jaariyah), beneficial knowledge, or a righteous son who will pray for him.” Narrated by Muslim (1631).
It was narrated from Abu Hurayrah (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said: “Allah, may He be blessed and exalted, may raise a man in status, and he will say, How did this come to me? Allah will say: By your son’s supplication for you.” Narrated by at-Tabaraani in ad-Du‘aa’ (p. 375); attributed by al-Haythami in Majma‘ az-Zawaa’id (10/234) to al-Bazzaar; also narrated by al-Bayhaqi in as-Sunan al-Kubra (7/78).
Adh-Dhahabi said in al-Muhadhdhab (5/2650): Its isnad is qawiy. Al-Haythami said: Its men are the men of as-Saheeh, apart from ‘Aasim ibn Bahdalah, who is hasan in hadith.

Giving charity on his behalf.
Performing Hajj and ‘umrah on his behalf, and dedicating the reward thereof to him.

We have already discussed these issues in detail on our website, in the answer to question no. 12652.

Paying off his debts

As Jaabir did for his father ‘Abdullah ibn Haraam (may Allah be pleased with them both), on the instructions of the Prophet (blessings and peace of Allah be upon him). The story was narrated by al-Bukhaari (2781).
With regard to what he missed of fasting Ramadan and giving zakaah, his son cannot make up for it. If a Muslim deliberately falls short in these two obligatory duties, then he must inevitably carry the burden of sin for that, and no one can do them on behalf of another.
Similar to that is the case of prayer; no one can pray on behalf of another.
Our Lord, may He be glorified and exalted, has told us that the Muslim will be requited for his deeds; if his deeds are good, then the requital will be good, and if they are bad, then it will be bad.
Allah, may He be exalted, says (interpretation of the meaning):
“So whoever does an atom's weight of good will see it,
And whoever does an atom's weight of evil will see it”
[az-Zalzalah 99:7-8].
But Allah may overlook bad deeds by His mercy and grace.
However, zakaah is like a debt: it rightfully belongs to those who are entitled to zakaah. So you should work out the zakaah that your father did not give whilst he was alive, and give it on his behalf, and we hope that that will be a means of relief for him.
We ask Allah to reward you with good for your love for your father and your keenness to honour him, and we ask Allah to pardon him.
And Allah knows best.