Sarah Aleem, Meggie de Castro, Susanne Geiger, Tasneem Atik-Sabri, and Tasneem Siddiqui wrote a great article discussing the Imam Zamin custom. It was part of the Anthropology of Money in Southern California exhibition. The exhibition covers the uses of money and money-like objects in the cultural, religious or ritual practices of various communities of Los Angeles and Orange Counties. Below is a small exert, be sure to read the entire essay.

The Imam gave this guarantee to everyone, establishing his name as Imam Zamin, the Imam of guaranteeing. Then, Ma’moun ordered the state mint to engrave the name of Imam Ridha on the state coins. Now the name of the 8th Imam had come in the coin so during journeys such coins were kept with the person’s body as a powerful symbol against any sort of calamities. So the Imam became a symbol of guaranteeing safe journey.

Thus, during the time period of Imam al-Ridha’s life marked the start of the practice of “Imam Zamin”. It become customary for people at this time to take the coin that had Imam al -Ridha’s name on it and wrap it around their arms when traveling. It was believed that when a person traveled with the Imam’s name, he would also be protected by the Imam’s blessings on his journey. When a person arrived safely to their destination they would take the coin and give it away as sadaqa, charity, in the name of the Imam al-Ridha. The practice of Imam Zamin has this name (zamin means safety) because it relates to Imam al-Ridha who is a protector and guarantee of a safe journey.

The act of Imam Zamin is in essence a type of nithr. A nithr is a promise to Allah that a person will perform some type of religious act if certain hajaat, or needs they have, are met. In the case of Imam Zamin, Muslims make a promise to Allah that if they arrive to their destination safely with the blessing of the holy Imam, they would then give away the coin they carried on their journey and give as charity. Nithr, however can be performed in a multiple of ways. For example, some Muslims will make a promise to Allah to fast a certain amount of days if they are healed from a bad illness.