7 is the Christian number of perfection

 Some Christians view 777 as the number of “ completion” or God's number. This is believed because “Satan's” number (better known as the mark or number of the “ beast” )is 666. But also because of the 7 seals 7 trumpets and 7 judgements (known as the bowl judgements) described in the book of Revelations.

Also because of the Biblical repetition of the number 7. Creation 7 days, the rather unorthodox campaign against Jericho 7 days and 7 times around the wall on the 7th day, and remember the years for planting was to be 6 and the land was to rest on the 7th year( also known as a Sabbath year).