He entered ihram for Hajj then missed the standing in ‘Arafah

Firstly: 

Standing in ‘Arafah is one of the pillars or essential parts of the Hajj; in fact it is the major pillar, because the Messenger (blessings and peace of Allah be upon him) said: “Hajj is ‘Arafah; whoever comes [to ‘Arafah] on the night of ‘Arafah, before dawn breaks on the night of Jam‘ [Muzdalifah] has completed his Hajj.” Narrated by at-Tirmidhi (889) and an-Nasaa’i (3016). Classed as saheeh by Shaykh al-Albaani (may Allah have mercy on him) in Saheeh an-Nasaa’i. Whoever does not come to ‘Arafah before dawn breaks on the Day of Sacrifice, even for a moment or passing through, has missed out on Hajj, according to scholarly consensus. 

An-Nawawi (may Allah have mercy on him) said in al-Majmoo‘ (8/273): If he enters ihram for Hajj, but does not stand in ‘Arafah until dawn breaks on the Day of Sacrifice, he has missed out on Hajj, according to scholarly consensus. End quote. 

Secondly: 

The one who misses out on Hajj – and had not stipulated a condition when first entering ihram, that his exiting ihram would be at the point where he was prevented from continuing – must do a number of things: 

1.He must exit his ihram by doing ‘umrah

2.He must make it up the following year, even if the missed Hajj was voluntary.

3.He must offer a sacrifice as well as making it up.

4.He must repent if there was no excuse for his delay. 

This is a summary of what the one who misses Hajj must do. 

Explanation of these points with evidence is as follows: 

1.The one who missed out on Hajj must exit his ihram by doing tawaaf and sa‘i, and cutting his hair or shaving his head (‘umrah) 

That is because of the report narrated by Maalik in al-Muwatta’ (870), that Abu Ayyoob al-Ansaari (may Allah be pleased with him) set out for Hajj, then when he was in an-Naaziyah, on the way to Makkah, he lost his mount. He came to ‘Umar ibn al-Khattaab (may Allah be pleased with him) on the Day of Sacrifice and told him what had happened. ‘Umar said: Do what those who do ‘Umrah do, then you will have exited your ihram. Then when Hajj comes next year, do Hajj and offer whatever sacrificial animal you can afford. Its isnaad was classed as saheeh by an-Nawawi (may Allah have mercy on him).

See: al-Muntaqa Sharh al-Muwatta’ (3/7); al-Majmoo‘ (8/274) 

2. With regard to its being obligatory to make up that Hajj and offer a hadiy (sacrificial animal) 

that is because of the report narrated by ‘Ikrimah, who said: I heard al-Hajjaaj ibn ‘Amr al-Ansaari say: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever breaks a bone or becomes lame has exited ihram, but he must do Hajj the following year.” ‘Ikrimah said: I asked Ibn ‘Abbaas and Abu Hurayrah about that and they said: He is telling the truth. Narrated by Abu Dawood (1862). According to another version: “Whoever breaks a bone or becomes lame or falls sick.” Classed as saheeh by al-Albaani in Saheeh Abi Dawood. 

That is also because of what ‘Umar said to Abu Ayyoob al-Ansaari (may Allah be pleased with them both): “Then when Hajj comes next year, do Hajj and offer whatever sacrificial animal you can afford.” 

This is the view of the Hanafis, Maalik, ash-Shaafa‘i and the Hanbalis. 

Maalik narrated from Naafi‘, from Sulaymaan ibn Yasaar, that Habbaar ibn al-Aswad came on the Day of Sacrifice when ‘Umar ibn al-Khattaab was offering his sacrifice, and said: O Ameer al-Mu’mineen, we miscounted the days and we thought that today was the day of ‘Arafah. ‘Umar said: Go to Makkah and do tawaaf (and sa‘i), you and the people with you, and slaughter the sacrificial animal, if you have one, then shave your head or cut your hair, and go home. Then next year, do Hajj and offer the sacrifice; whoever cannot afford it, let him fast three days during Hajj and seven days after he has returned home. 

See al-Majmoo‘ (8/275) 

Ibn Qudaamah said in al-Mughni (3/280):

The sacrifice is required of the one who misses Hajj, according to the more correct of the two reports. This is the view of those whom we have named among the Sahaabah and fuqaha’, apart from ashaab ar-ra’y, who said that he does not have to offer a sacrifice. In support of our view, we have the hadith of ‘Ata’ and the consensus of the Sahaabah. End quote. 

He also said (3/281):

If he has brought a hadiy (sacrificial animal) with him, he should sacrifice it [i.e., in the year in which he missed Hajj], that does not take the place of the sacrifice he has to offer in the following year. Rather in the following year he must also bring a hadiy. This was stated by Ahmad. That is because of the hadith of ‘Umar (may Allah be pleased with him). End quote. 

See also al-Majmoo‘ (8/275) 

3.In the rulings mentioned above there is no differentiation between the one who has a legitimate excuse and the one who does not, but there is a difference between them in terms of sin; the one who has an excuse is not sinning, whereas the one who has no excuse is sinning. This was clearly stated by al-Qaadi Abu’t-Tayyib and others. See al-Majmoo‘ (8/276) 

And Allah knows best.