About three hours after docking, at 19:19 UTC, Tom Stafford and Alexei Leonov shook hands in the open hatch between the ships — the first handshake of two nations in space. Television carried it around the world as a symbolic end to the space race.
The ships stayed joined for nearly two days (about 44 hours). During that time the crews visited one another four times, exchanged flags and gifts, shared meals and carried out a series of joint experiments — from observing the Sun during an artificial eclipse (Apollo shaded the Sun for Soyuz) to biological and materials tests. Stafford spoke Russian and Leonov English; Leonov later joked that Stafford's drawling Russian was "Oklahomski".
From the flight transcript
Glad to see you. Very, very happy to see you.
NASA — The Apollo-Soyuz Mission · NASA NSSDCA — Apollo-Soyuz Test Project · Spaceline — ASTP Mission Fact Sheet — full list on Apollo–Soyuz