Abba John the Dwarf:

Abba John the Dwarf said, 'A house is not built by beginning at the top and working down. You must begin with the foundations in order to reach the top.' They said to him, 'What does this saying mean?' He said, 'The foundation is our neighbour, whom we must win, and that is the place to begin. For all the commandments of Christ depend on this one.'