Shiva Purana
परमेष्ठिगुरुं ध्यायेत्सांबबुद्ध्या स्वनामतः ॥ गुरुश्च परमन्तस्मात्परापरगुरुं ततः ॥ ७ ॥
He shall then meditate on Parameṣṭhi Guru as Sāmba with his own name. Paramaguru and Parāt Paraguru shall also be meditated upon.
english translation
parameSThiguruM dhyAyetsAMbabuddhyA svanAmataH ॥ guruzca paramantasmAtparAparaguruM tataH ॥ 7 ॥
hk transliteration by Sanscript