In Quran in many verses God makes it clear that payment of zakat is compulsory.

Could you please quote some verses that make payment of zakat compulsory?

God also tells us it is to be paid on the day of harvest (i.e. When income is received)

I guess if you are referring to 6141 then I do not see the word zakat in this verse.

it is to be paid to the parents/relatives, orphans, travelling alien and the poor.

If you are referring to 2177 then it says
Righteousness is not that you turn your faces toward the east or the west, but righteousness is one who believes in Allah , the Last Day, the angels, the Book, and the prophets and gives wealth, in spite of love for it, to relatives, orphans, the needy, the traveler, those who ask , and for freeing slaves; establishes prayer and gives zakah; fulfill their promise when they promise; and are patient in poverty and hardship and during battle. Those are the ones who have been true, and it is those who are the righteous.

The red part says gives wealth not zakat.

The amount is given in sura 2219 they also ask you what to give to charity, say, "the excess".

There is no amount given in this verse. It says keep open (spend) whatever can be spared.

In Sura 1726-29 God tells us not to be excessive or extravagant.

The word used here is tubazzir which gives sense of wasting and not of spending on good cause.

Peace

If you carefully revisit the arabic text, the term used in "ibnus saeel", or literally "sons of the path". "Travelling alens" is a mere figurative translation. We should put more emphasis on the original arabic phrase to determine who qualifies for this label.

Per my humble understanding anyone who is dependent on whatever help he can get from the people who he meets on the path (in his journey) qualifies for the label "sons of the path".

The poor (masakeen) is always in the verse where ibnus sabeel are mentioned. So, it appears to me this extra term covers anyone who is not necessarily poor (miskeen) in terms of net wealth, but has fallen into a dire situation because of circumstances.

Taking masakeen and ibnus saeel together all people in need are covered.

May Allah guide us all to the straight route.

Regards,
Arman

In our country there was a belief that to giving feast to strangers is ones duty. There are moral stories that talks about it.
People voluntarily invite those people to their house for the feast when they come to their place/village.

Its good thing, since that these monks/wanderers also bring with them new knowledge which will be shared with the people at home.

I would love to see a household taking in a stranger for dinner and staying overnight today. People are just suspicious and wary about others today in general.

Perhaps it remains in Eastern Asia yet concerning hospitality.

People in Iran are too concerned by the dogmatic religious doctrine and government that they would not allow a stranger or fellow brother into their home except for a brief visit. But the friendliness towards family and relatives is abundant almost exaggerated in comparison. It seems people only care to their own kin.

Traveling alien could include a wanderer, a person who has no residence here yet is stuck here. In the past when travels took a long time it was perhaps a caravan you would offer shelter to, but you can still help by giving a stranger a coin or even volunteer to help homeless. I think active helping is better than just giving a coin.

Regarding zakateh, my current understanding is that it is not related to paying money alone, but it is good deeds in general. That can also be reinforced by the traveling alien which may not have needed money but rather shelter during their journey.

Zakateh refers to purification and by that is performing goodly deeds. By doing good you can elevate your soul, especially if you expect nothing in return.

Salaam

Abraham seems to do the same practice..
The story appeared on few places in the Quran..
He slaughtered his calf to feed 'the traveling alien' who appeared at his house...
As it turns out the 'traveling alien' doesn't need any food as they're apparently 'not from this earth'..