Grube had been born in Walscheben (near Erfurt), Germany and was a distant relative of Wolphert Gerretse van Kouwenhoven, founder of the New Netherlands colony, which included modern-day New York City. (Presidents Theodore and Franklin D. Roosevelt are also descendants of van Kouwenhoven.) Grube was educated in the University at Jena, and had came to the United States in 1746 at the age of 31. At Bethlehem, Grube had served as the private tutor to the sons of Thomas Noble, a wealthy merchant.
His appointment to Meniolágoméka appears to have been his first engagement as a missionary. After arriving there, Grube set himself to learning the Delaware dialect and holding classes for the Indian children, who, he recorded, were very eager to learn. But there may have been a thing or two he could have learned from the Indians as well: on the third day after his arrival, while trying to cut wood, he missed the tree and delivered himself a serious blow to his left leg. The injury left him incapacitated in his cold little hut, where he lay with a wooden bowl as a pillow. During his convalescence, however, he began the task of translating the New Testament into the Delaware language, and he taught the children some German chorales. When Spring came, the men of the village fetched new bark peelings to make the roof of Grube's hut watertight, and to "re-side" the hut. In contrast to their own huts, however, they left Grube a small window, so that he could have light for his reading and writing.
Already by Summer, however, the Moravian leadership decided that Grube was needed elsewhere, and they chose to replace him. They sent David Zeisberger to fetch Grube back to Bethlehem. It was a melancholy occasion, but Grube tried to cheer his new friends by announcing that the day before his departure they would celebrate a traditional Moravian "Love Feast," and he promised hot chocolate for everyone. As he and Zeisberger made their way back to Bethlehem, the lads from the village walked him to the top of the Blue Mountain. This would not be the last time they saw Grube -- but they could not have known the trials and hardships that they would suffer before they met him again.