SB 12.3.18

śrī-śuka uvāca
kṛte pravartate dharmaś
 catuṣ-pāt taj-janair dhṛtaḥ
satyaṁ dayā tapo dānam
 iti pādā vibhor nṛpa
Word for word: 
śrī-śukaḥ uvāca — Śrī Śukadeva Gosvāmī said; kṛte — in the Satya-yuga, the age of truth; pravartate — exists; dharmaḥ — religion; catuḥ-pāt — with four legs; tat — of that age; janaiḥ — by the people; dhṛtaḥ — maintained; satyam — truth; dayā — mercy; tapaḥ — austerity; dānam — charity; iti — thus; pādāḥ — the legs; vibhoḥ — of mighty religion; nṛpa — O King.
Translation: 
Śukadeva Gosvāmī said: My dear King, in the beginning, during Satya-yuga, the age of truth, religion is present with all four of its legs intact and is carefully maintained by the people of that age. These four legs of powerful religion are truthfulness, mercy, austerity and charity.
Purport: 

Just as there are four seasons, there are four ages of the earth, each lasting hundreds of thousands of years. The first of these is Satya-yuga, when such good qualities as charity are prominent.

Actual charity, here referred to as dānam, is to award fearlessness and freedom to others, not to give them some material means of temporary pleasure or relief. Any material “charitable” arrangement will inevitably be crushed by the onward march of time. Thus only realization of one’s eternal existence beyond the reach of time can make one fearless, and only freedom from material desire constitutes real freedom, for it enables one to escape the bondage of the laws of nature. Therefore real charity is to help people revive their eternal, spiritual consciousness.

Religion is here referred to as vibhu, “the mighty,” because universal religious principles are not different from the Supreme Lord Himself and ultimately lead one to His kingdom. The qualities mentioned here — truthfulness, mercy, austerity and charity — are universal, nonsectarian aspects of pious life.

In the First Canto of Śrīmad-Bhāgavatam, the fourth leg of religion is listed as cleanliness. According to Śrīla Viśvanātha Cakravartī Ṭhākura, this is an alternative definition of the word dānam in the present context.