Furthermore, there is great and profound wisdom behind this Sunnah – i.e. the Sunnah of praying in an open area of land (i.e. the musallaa). And it is that:
The Muslims will have two days out of the year where all the people of every city can gather together – whether men, women or children – and turn towards Allaah with their hearts in unity, praying behind one Imaam, making the takbeer and the tahleel and supplicating to Allaah sincerely together, as if they were united upon the heart of one man, happy and joyous about the blessing Allaah has bestowed on them. So the ‘Eid will truly be an occasion of celebration for them.
Allaah’s Messenger صلى الله عليه وسلم ordered the women to go out to pray ‘Eid along with the people, and he did not make an exception for any of them. This is even to the point that he made no excuses for those women who did not have a garment by which they could veil themselves when coming out, as instead he commanded them to borrow garments from other women. And this is even to the point that he صلى الله عليه وسلم commanded those women who had a reason that prevented them from praying (i.e. menses) to go out to the musallaa, so that they may “witness the good and the supplication of the Muslims.”
The Prophet صلى الله عليه وسلم, and then his Khaleefahs (successors) after him, and the delegated leaders in the cities would lead the people in prayer. Then they would give them a sermon saying that which would admonish them. And they would teach them what would be of benefit to them in this world and in the Hereafter. And they would order them to give in charity in that gathering. So the rich person would show affection towards the poor person. And the poor would find joy in what Allaah has given them from His Bounty during this blessed assembly, which Allaah’s Mercy and Contentment descends upon.
So it is only proper for the Muslims to respond to following the Sunnah of their Prophet and reviving the rites of their Religion, which is the point of their resolution and success.
“O you who believe! Respond to Allaah and to the Messenger when He calls you to that which will revive you.” [Surah Al-Anfaal: 24]
Shaikh Waliyullaah Ad-Dihlawee said in Hujjatullaah-il-Baalighah under the heading “The Two ‘Eids” (2/30-32):
“The foundation with regard to them is that every nation has a day in which they beautify themselves and go out from their city with their adornment. This is a custom, which no group amongst the Arabs and non-Arabs have stopped practicing. When the Prophet صلى الله عليه وسلم came to Madeenah, he found that the people had two days in which they would go out and enjoy themselves, so he said: ‘Allaah has replaced these two days with something that is better than them – the Day of Adhaa and the Day of Fitr.’  It was said that these two (prior) days of celebration were: An-Nayrooz and Al-Mahrajaan. These two days were only replaced because there is no ‘Eid for a group of people except that the reason for its existence is to elevate the rites of a Religion or to comply with the founders of a particular way or something that resembles that. So the Prophet feared that if he were to leave them with their custom, there would remain this elevating of the rites of Jaahiliyyah (i.e. the Days of Ignorance) or the propagating of the (false) ways of the ancestors. So he صلى الله عليه وسلم replaced them with two days in which there was found an elevating of the rites of the pure and upright Religion (of Islaam). And along with adorning oneself for the occasion, he صلى الله عليه وسلم included the remembrance of Allaah as well as various acts of obedience, so that the gathering of the Muslims won’t just be for pure play and enjoyment, and so that no gathering from them will be void of raising Allaah’s Word.
The first of these two days is ‘Eid-ul-Fitr, the day when they end their fasting and give a certain type of their Zakaat. So they experience this ‘natural joy’ that is caused by their withdrawing from conditions that were difficult upon them (i.e. the fast). And the poor person experiences joy at taking his charity.
The ‘intellectual joy’ they experience is due to the delight of knowing that Allaah has blessed them with the ability to complete what He made obligatory upon them (i.e. the fast)…
The second is the day when Ibraaheem (intended to) sacrifice his son Ismaa’eel, may Allaah be pleased with both of them. But Allaah blessed them both by replacing him with the great sacrifice (i.e. a ram). This is since on this day, one can be reminded and take heed of the condition of the ancestors of this noble and upright religion, by sacrificing one’s soul and wealth in obeying Allaah, and having firm patience. In this, there is a similarity to those performing Hajj, where one tries to emulate them and longs to be in the state they are in. This is why it is legislated to make the Takbeer in it, which is found in Allaah’s saying:
‘And so that you may magnify Allaah (by making Takbeer) for having guided you and so that you may be grateful.’ [Surah Al-Baqarah: 185; Surah Al-Hajj: 37]
This means: Give thanks to Him for granting you the ability to fast. This is why performing the sacrifice and saying the takbeer out loud were legislated on the Days of Minaa. And this is why it is recommended for those who intend to offer the sacrifice to abandon shaving (the body hair).  And this is also why the Prayer and the Khutbah (sermon) were prescribed – so that no part of their gathering could be void of the remembrance of Allaah and the elevating of the rites of the Religion.
Another objective from the objectives of the Pure Legislation is included in this, which is that: Every nation must have some presentation, in which its people gather together during it to display their strength and to show their numbers. This is why it is recommended for everyone to go out (to the musallaa) – even the children, the women, the young girls and the menstruating women. However, they (i.e. menstruating women) must not join the musallaa (i.e. the prayer) but rather witness the supplication of the Muslims.
And it is also why the Prophet صلى الله عليه وسلم would vary in the roads he took when going and coming from the musallaa, so that the people in each of the roads would see the strength of the Muslims. And since the origin of ‘Eid was to decorate and adorn oneself, it is recommended to wear one’s best garment, to enjoy oneself (taqlees),  to take different routes when going and coming and to go out to the musallaa.”
 I say: Ahmad and others reported it with an authentic chain of narration. I have referenced it in as-Saheehah (no.2021).
 I say: He is indicating the Prophet’s statement: “When the Hilaal (crescent) for Dhul-Hijjah is sighted and one of you wants to offer a sacrifice, then he must refrain from cutting his hair and nails.” And in one narration: “…then let him not cut any part of his hair or nails until he offers the sacrifice.” [See Mukhtasar Saheeh Muslim (no. 1251) and others] I say: It is apparent from the hadeeth that anyone who is determined to perform the sacrifice is obligated not to cut his hair and nails until he offers the sacrifice. So this type of cutting mentioned above is forbidden. Imaam Ahmad and others held this view. So let those who are tested with shaving their beards take note of this, for indeed, there are three sinful matters in their shaving of their beards for the day of ‘Eid:
First: The shaving itself, for it is a feminine trait, an imitation of the disbelievers, and an alteration of Allaah’s creation, as I have explained in my book “Adaab az-Zafaaf fis-Sunnah al-Mutahharah (Sixth Edition, pg. 118).
Second: Adorning oneself for the day of ‘Eid by disobeying Allaah.
Third: What is derived from this hadeeth of the forbiddance of cutting the hair for the one who intends to offer the sacrifice. In reality, there are very few people that are saved from committing this (sin), even some of the people of knowledge (do it)! We ask Allaah to protect us.
 Shaikh Ad-Dihlawee said in his footnote: “Taqlees (Enjoying oneself) means beating the duff and playing when the kings arrive, in order to welcome them.” I say: He is indicating the hadeeth that has been reported by Ibn Maajah (1/391) and others with two chains of narration. In one of them is Shareek, who is Ibn ‘Abdillaah Al-Qaadee – he had bad memory. And in the other chain is found Abu Ishaaq, who is As-Subay’ee – he would mix up his narrations. At-Tahaawee weakened it in his Mushkil-ul-Athaar (2/209-210) based on two angles, so refer to it if you wish.
Source: Al-Ibaanah EBook –Praying Eid in the Musallaa is the Sunnah- Shaykh al Albanee