Mordechai was born on 1 January 1931 in Krakow to his parents Aryeh Leib Schreiber and Penina (Pearl) née Lankowitz. His family made aliyah when he was one year old and settled in Tel Aviv. His father at first worked in construction, then in real estate. Aside from Mordechai, the family had another son. He studied in the Carmel Elementary School and then in the New High School.
In 1944, he joined Lehi. His father opposed this, and they fought about it. At fifteen, he left his parent’s home and moved into his girlfriend’s house. His mother brought him food, clothing and some money. At first, like other young men and women, he put posters and disseminated promotional materials.
Later, he joined the combat brigade, and when he was just sixteen, on 9 August 1947, he was arrested after blowing up the tracks near Wilhelma. A court marital in Jerusalem found him guilty of shooting at the police as well, in addition to carrying live weapons. At the end of November of that year, shortly before the UN announced the Partition Plan, he was sentenced to life imprisonment. Only his youth saved him from a death sentence. He was transferred from Jerusalem Central Prison to Atlit, and was released when the State was established.
Mordechai enlisted in the IDF, serving in the Intelligence Corps in the section for studies of the Land of Israel. In his reserve duty and his civilian life, he continued to delve into this subject, his favorite.
After his demobilization, he completed his matriculation and went to study geography in Hebrew University. He was also a youth guide in the Ein Kerem Agricultural School. In 1958, he started working as a tour guide. He also lectured in a tourism school in Jerusalem and trained tour guides. He was one of the prominent personalities in studies of the Land of Israel and a tour guide par excellence.
In 1950, he married Miriam Levi, a kindergarten teacher, superintendent and director of parents’ groups. She was also a Lehi member, known as Drora. In 1958, they lived in the Ein Kerem Agricultural School, and then they moved on to the Beit Zayit settlement. Mordechai identified a dinosaur fossil in the settlement, making it a tourist destination. He even received academic recognition for his discovery.
The couple had three sons, Shai, Nir and Assaf, as well as numerous grandchildren.
Mordechai passed away on 28 Sivan 5755, 26 June 1995, and was buried in Beit Zayit
His expansive professional library was given to the Ammunition Hill Museum in Jerusalem. The Municipality of Jerusalem decided to name a street after him. The sign reads: “Motke Sofer — geographer, historian, and lover of the land of Israel (5691-5755).”