जायमानो वै ब्राह्मणस्त्रिभिर् ऋणवा जायते ब्रह्मचर्येण ऋषिभ्यो यज्ञेन देवभ्यः
प्रजया पितृभ्य एष वा अनृणो यः पुत्री यज्वा ब्रह्मचारिवासी
A Brahmana on birth is born with a threefold debt, first one is to the Rishis (Rishi Rina); second one is to the devatas (Deva Rina); and the third one is to the ancestors (Pitru Rina). He is freed from his first debt who lived as a Brahmachari, he is freed from the second debt by peforming Yajnas, and the third debt can be fulfilled by begetting a son.
Now, in order to repay the second and third debts, one has to marry as without wife no one is allowed to perform sacrifices and without wife one cannot beget a son. As Naishtika Brahmacharis and Smartha Sanyasis never marry, how do they repay the second debt and third debt?