Can you give me some examples of situations where a man is excused from attending the mosque for Fajr prayer? What distance is too far? What constitutes too much hardship? Is there any difference between the obligation on men to attend the mosque for the other 4 prayers?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Praying in congregation is compulsory for men. This is the prevailing opinion of the Muslim scholars based on sound Ahadeeth. This ruling applies for all five prayers even though there are Ahadeeth stating the great reward of praying in congregation for certain prayers in particular.

Some Ahadeeth state particularly the excellence of performing the Fajr Prayer in congregation.

The Prophet said: “He who observed the ‘Isha prayer in congregation, it was as if he prayed up to midnight, and he who prayed the Fajr prayer in congregation, it was as if he prayed the whole night.” [Muslim]

The mentioned excellence of Fajr Prayer is because the angels of the night and the angels of the day gather at the time of this prayer.

Allah Says (what means): {Establish prayer at the decline of the sun [from its meridian] until the darkness of the night and [also] the Qur'an of dawn. Indeed, the recitation of dawn is ever witnessed.} [Quran 17: 78]

As for the distance which could be a liable excuse for not praying in congregation, it is the point from which the Athaan is called without using loudspeakers to the point where it cannot be heard when it is calm, and there is nothing preventing the Athaan being heard if it is announced without the use of loudspeakers.

Every man who hears the Athaan should respond to it. He should always pray in congregation and pray the Jumu’ah Prayer unless he has a legal excuse, such as illness etc. The Prophet did not go to the mosque when he was ill, though his house was beside his mosque. It is narrated in Saheeh Muslim that Ibn Mas’ood, may Allaah pleased with him, said: “I have seen the time when no one stayed away from the Prayer except a hypocrite, whose hypocrisy was well known, or a sick man, but if a sick man could walk between two persons (i.e. with the help of two persons, one on each side) he would come to the Prayer.” It is permissible for one not to attend congregational Prayer if the meal is presented or he needs to answer the call of nature. The Prophet said: “There is no prayer when the meal is presented nor when one needs to answer the call of nature.” [Muslim]

The above-mentioned ruling also applies in case of fear of money or other precious objects being stolen. For details you may refer to the Books of Fiqh. But the general ruling for not attending the congregational Prayer is every situation in which attending it becomes hard or unbearable, such as in the case of rain, extreme cold, illness, or for fear of losing property or being killed.

Know that the greater the distance to the mosque, the greater the reward you receive for going there to perform the Prayer. Imam Al-Bukhaari reported that the Prophet said: “The one who gets the greatest reward for a Prayer is the one who walks the farthest distance.”

Ubay ibn Ka’b narrated that there was a man, and I do not know of any other man whose house was farther than his from the mosque, and he never missed the prayer (in congregation). It was said to him or I said to him: “If you were to buy a donkey you could ride upon it in the dark nights and in the burning sand.” He said: “I do not like my house to be situated by the side of the mosque, for I (eagerly) desire that my steps towards the mosque, and back from it, should be recorded when I return to my family.” Upon this, the Prophet said: “Allah has indeed gathered all that (reward) for you.” [Muslim]

For more benefit on praying in congregation at home if one is exempted from praying in the mosque, please refer to Fataawa 295357, 89364, 82264, 83356 and 83739.

Allah knows best.