When the Egyptians were chasing the Israelites, Rashi says they did so "with one heart as one man" (Shemot 14:10):
נסע אחריהם: בלב אחד כאיש אחד
When the Israelites stood at the foot of Har Sinai, he uses a similar language (Shemot 19:2) except that the language is switched to "as one man with one heart":
ויחן שם ישראל: כאיש אחד בלב אחד
Why the difference?