Details

Property values; @extend, @include, and @import directives; and variable declarations should always end with a semicolon.

Bad: no semicolon

p {
  color: #fff
}

Bad: space between value and semicolon

p {
  color: #fff ;
}

Good

p {
  color: #fff;
}

CSS allows you to omit the semicolon if the statement is the last statement in the rule set. However, this introduces inconsistency and requires anyone adding a property after that property to remember to append a semicolon.