Kathir bin Qais narrates:

I was sitting with Abu Darda radhiyallah hu anhu (ra) in a masjid in Damascus, when a person came to him and said; “O, Abu Darda ra, I have come all the way from Madinah to learn one Hadith from you, as I understand you have heard it directly from the Prophet Muhammad saw (peace be upon him).”
Abu Darda ra: “Do you have any other business in Damascus?”
The Person: “No.”
Abu Darda ra: “Are you sure that you have no other work in Damascus?”
The person: “I have come to this place with the sole purpose of learning Hadith.”
Abu Darda ra: “Listen. I have heard the Prophet Muhammad saw (peace be upon him) saying; ‘Allah eases the way to Paradise for one who traverses some distance to seek knowledge. The angels spread their wings under his feet, and all things in heavens and earth (even the fish in the water) pray for his forgiveness, The superiority of a person processing knowledge over a person doing worship is a the superiority of the moon over the stars. The Ulama are the inheritors of the Prophet Muhammad saw (peace be upon him). The legacy of Prophets Alaihimussalaam is not neither gold nor silver. Their legacy is knowledge. A person who acquires knowledge acquires a great wealth.”
Abu Darda ra is foremost among the Companion who possessed very sound knowledge in religion. He is called ‘Hakim ul Ummah’ – the Sage of Islam. He once said:

“Before Islam, I lived on trade. After accepting Islam, I tried to combine the service of Allah swt with my business, but I could not do so. I therefore gave up business and devoted myself solely to the service of Allah swt. Now, if I have a shop at the gate of a masjid and have no fear of losing a single Solat thereby, and even if the shop gives me daily profit of 40 dinars to spend the whole lot in the path of Allah swt, even then I am not willing to turn business.”

Somebody inquired the reason. He replied:
“Because of the fear of reckoning.”

He used to say:
“I love death, so that I may meet Allah swt. I love destitution, so that I will be meek. I love sickness, so that I will be pardoned my sins.”
In this story, we find a person travelling all the way from Madinah to Damascus for the sake of one Hadith. This was not at all hard for those people. Sha’abi rahmatullah alaihi is a famous Muhadith of Koofa. He once narrated a Hadith to one of his students and said:

“You are listening to this Hadith while sitting in your home town. People had to travel all their way to Madinah for even less important things, because Madinah was the only of seat learning in those days.”
Saeed Ibnul Musayyab rahmatullah alaih is a famous Tabi’ee. He says:

“For each Hadith that I have learnt, I had to travel on foot for days and nights together.”

Imam Bukhari Rahmatullahi alaih (Rah a) was born in the Islamic month of Shawal 194 A.H. He started learning Haditf in 205 A.H. i.e., when he was only eleven. He had memorized all the books written by Abdullah bin Mubarak (Rah a) while he was in his early teens. After collecting Hadith from all the learned men of his own locality, he set out in 216 A.H. in search of further knowledge. His father died and he could not leave his widowed mother alone. He therefore took her with him on his long and strenuous journey to Balkh, Baghdad, Makkah, Basra, Koofah, Asqalan, Hims and Damascus. He collected all the available Hadith from these seats of learning. He was accepted as an expert in Hadith, while he had no single hair on his chin.

Hashad (Rah a) and one of his Companions said:

“Bukhari and we two used to go together to the same teacher. We noted down all the Hadith that we learnt, but he wrote nothing. After many days we said to him, ‘Bukhari, you are wasting your time.’ He kept quiet. When we admonished him again and again, he said, ‘you are now annoying me too much. Bring your notes.’ We brought our notes, which covered about 15,000 Hadith. He, to our utter amazement, recited all those Hadith by heart.”