In plain words
But a gift given in expectation of return or a result, and given reluctantly, is remembered as rājasa.
Word for word
But what is given for a return of service, or again aiming at fruit, and [is] given with vexation, that dāna is held [to be] rājasa.
यत् तु प्रत्युपकारार्थं फलमुद्दिश्य वा पुनःदीयते च परिक्लिष्टं तद् दानं राजसं स्मृतम्
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam· bhāṣya
यत्तु दानं प्रत्युपकारार्थं काले तु अयं मां प्रत्युपकरिष्यति इत्येवमर्थम् , फलं वा अस्य दानस्य मे भविष्यति अदृष्टम् इति, तत् उद्दिश्य पुनः दीयते च परिक्लिष्टं खेदसंयुक्तम् , तत् दानं राजसं स्मृतम् ॥ २१ ॥
In plain words
But some giving has a hook in it. It is given for the return favour — 'when the time comes, this man will do the same for me' — or for the fruit nobody can see: 'something will come back to me later from this gift.' Given with that in view. And given grudgingly besides, the whole act pinched with regret. Giving like that is called rājasic.
Close to the Sanskrit
But that gift which is for the sake of a return favour — with the thought, 'This man will at the proper time do a favour for me in return' — that is, for such a purpose; or, 'An unseen fruit of this gift will come to me' — and which, aiming at that, is moreover given grudgingly, that is, joined with regret: that gift is declared to be rājasic.