aham evāsam evāgre
nānyad yat sad-asat-param
paścād ahaṁ yad etac ca
yo 'vaśiṣyeta so 'smy aham
aham - I, the Personality of Godhead; eva - certainly; āsam - existed; eva - only; agre - before the creation; na - never; anyat - anything else; yat - which; sat - the effect; asat - the cause; param - the supreme; paścāt - after; aham - I, the Personality of Godhead; yat - which; etat - this creation; ca - also; yaḥ - who; avaśiṣyeta - remains; saḥ - that; asmi - am; aham - I, the Personality of Godhead.
This is a quotation from Śrīmad-Bhāgavatam (2.9.33). It is the first verse of the catuḥ-ślokī. For an explanation see Ādi-līlā, chapter one, text 53.