It was the practice of the Prophet (peace and blessings be upon him):
"He (peace and blessings be upon him) would press his chest and face against the Multazam."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 5012
Hadith Gradingالألبانی:حسن
Hadith Takhrij[هق] عن ابن عمرو. الصحيحة ٢١٣٨: عبد الرزاق، د، هـ.