Spinach produces a poison called saponin, which can help protect strawberries from fungal diseases and pests.
Peas and beans fix nitrogen in the soil, which can spur spinach growth. They also cast needed shade for spinach in early summer.
These cool weather herbs thrive in the same conditions as spinach. Chives can also repel pests, while parsley and cilantro attract beneficial predatory insects.
for what not to plant with spinach & a spinach companion planting chart