Sadly that isn’t true. Gagarin’s first words in space were “The sky is very black. The Earth is blue. Everything can be seen, it is very clear”.

The line about “No gods” comes from an erroneous attribution of a Khrushchev quote to Gagarin which he supposedly said several days after his trip; however there is no evidence to back this up, which combined with the fact that Gagarin was an active member of the Orthodox Church, makes it unlikely that he ever said anything related to the line.