What is Yajna? How it is different from Tapas?
Can anyone give scriptural references which describes these two terms?
An explanation of Yajna is given here:
Tapas is the spiritual practice part of Hinduism, i.e., it includes both the Yoga and the nidhidhyasana practices. Tapas used to be translated as penance in the 19th century. Thus the word penance is used to indicate Tapas in the two passages below.
For them that perform the sacrifice of penance - the Yoga they endeavor to effect with Brahma is their ladle; the heart is their clarified butter; and high knowledge constitutes their Pavitra (couple of Kusa blades for sprinkling clarified butter upon the sacrificial butter). All kinds of crookedness mean death, and all kinds of sincerity are called Brahma
Mahabharata, Santi Parva, Section LXXIX
Bhishma said, 'The fruits, however, of penance directed towards the soul are obtainable in this world. whatever be the object to which one devotes oneself, that object, O Bharata, and nothing else, appears to one as the highest of acquisitions fraught with the greatest of blessings. When one reflects properly (one's heart being purified by such reflection), one comes to know that the things of this world are as valueless as straw. Without doubt, O Yudhisthira, which is full of defects, is so constituted, every man of intelligence should strive for the emancipation of his soul.'
Mahabharata, Santi Parva, Section CLXXIV
Sri K. M. Ganguli, the 19th century English translator comments about the second passage, 'It is very difficult to literally translate such verses. ..... Tapah is generally rendered penance. Here, however, it has a direct reference to sravana (hearing), manana ( contemplation) and nidhidhyasana ( abstraction of the soul from everything else for absolute concentration). '