Saruli Caretaker

• WOTC Official Reminder Textofficial rules
  Defender — This creature can't attack.

• WWizards of the Coast2019-01-25
  Official Ruling
  You can tap any untapped creature you control, including one you haven’t controlled continuously since the beginning of your most recent turn, to pay the cost of Saruli Caretaker’s activated ability. You must have controlled Saruli Caretaker continuously since the beginning of your most recent turn, however.

Rulings via Scryfall