Charity that is given with disdain, at the wrong time and place, to an unworthy beneficiary, is said to be in the mode of ignorance.
Bhagavad Gita - Chapter 17 - Shraddha Traya Vibhaga Yoga - The Yoga Explaining Three Types of Faith
The three words om tat sat are described by the Vedas to represent the Absolute Truth. In ancient times, the brahmanas, the Vedas and the process of sacrifice were manifested from these three words.
Thus, those that seek the Supreme always chant the syllable om when they commence sacrifices, give in charity, perform austerities and undertake other activities prescribed in the Vedas.
By uttering the word tat, those that aspire for liberation perform various types of sacrifices, austerities and charity without the selfish desire to enjoy the results.
The word sat indicates the nature of the Absolute as well as the sadhus that seek Him. Therefore, O Partha, the word sat is uttered during all virtuous activities.
Steadiness in the performance of sacrifices, austerities and charity is known as sat. Any activity that is performed for the Supreme is known as sat.
O Partha, any sacrifice, austerity, charity or activity that is performed without faith is known as asat – false. Such activities bear no auspicious results in this world or the next.