Brahmarpanam

Brahmārpañam Brahma Havir
 Brahmāgnau Brahmañāhutaṃ |

Brahmaiva Tena Gantavyam
 Brahmakarmā Samādhinah ||

Aham Vaishvānaro Bhutvā 
Prāñinām Ḍehamāshritaha |

Prāñāpāna Samāyuktah
 Pachāmyannam Chaturvidham ||

ब्रह्मार्पणं ब्रह्म हविः ब्रह्माग्नौ ब्रह्मणा हुतम् ।
ब्रह्मैव तेन गन्तव्यं ब्रह्मकर्मसमाधिना ॥

अहम् वैश्वानरो भूत्वा प्राणीनाम् देहमाश्रितः |

प्राणापान समायुक्तः पचाम्यन्नम् चतुर्विदम् ||

Brahmārpañam Brahma Havir
BrahmāgnauBrahmañāhutaṃ,

Brahmaiva Tena Gantavyam
BrahmakarmāSamādhinah.

The act of offering is God. The oblation is God. By God it is offered into the Fire of God.
God is That which is to be attained by him who performs action pertaining to God.

Word For Word Translation

brahmā: supreme spirit; arpañam: oblation, havih: butter,   agnau: in the fire of consummation.
      brahmana: by the spirit soul.   aahutam: offered.
brahma: spiritual kingdom:   eva: certainly.   tena: by him.  gantavyam: to be reached.
brahma: spiritual.  karma: in activities.   samadhina: by complete absorption.

AhamVaishvānaroBhutvā
PrāñināmḌehamāshritaha,

PrāñāpānaSamāyuktah
PachāmyannamChaturvidham.

Becoming the life-fire in the bodies of living beings, mingling with the subtle breaths
I digest the four kinds of food. 

Word For Word Translation

aham:   I. vaisvanarah: My plenary portion as the digesting fire.   bhutva: becoming.
praninam: of all living entities.   deham: in the bodies.   asritah: situated.
prana: the outgoing air.   apana: the down-going air.   samayuktah: keeping in balance.
pachami: I digest.   annam.   foodstuff.    catuh-vidham. the four kinds.

The two verses are from the Bhagavad Gita, Chapter IV, Verse 24 and 
Bhagavad Gita, Chapter XV, Verse 14. 

Sri Sathhya Sai Baba's explanation of this prayer

We should partake food with a sathwic (pure, serene) mind. Our ancestors recommended the offering of food to God before partaking. Food so partaken becomes prasad (consecrated offering). Prayer cleanses the food of the three impurities caused by the absence of cleanliness of the vessel, cleanliness of the food stuff, and cleanliness in the process of cooking. It is necessary to get rid of these three impurities to purify the food, for pure food goes into the making of a pure mind. It is not possible to ensure the purity of the cooking process because we do not know what thoughts rage in the mind of the man who prepares the food. Similarly, we cannot ensure the cleanliness of the food ingredients because we do not know whether it was acquired in a righteous way by the person who sold it to us. Hence, it is essential on our part to offer food to God in the form of prayer so that these three impurities do not afflict our mind.