When any petition has been filed seeking the involuntary commitment of a respondent and such petition has been reviewed by the probate judge, the probate judge shall order the sheriff of the county in which the respondent is located to serve a copy of the petition, together with a copy of the order setting the petition for a hearing, upon the respondent. Said notice shall include the date, time and place of the hearing; a clear statement of the purpose of the proceeding and the possible consequences to the subject thereof; the alleged factual basis for the proposed commitment; a statement of the legal standards upon which commitment is authorized; and a list of the names and addresses of the witnesses who may be called to testify in support of the petition. The hearing shall be preceded by adequate notice to the respondent.