Mahabharata Adi Parva Chapter 100:4

Mahabharata Adi Parva Chapter 100:4 Thou goest not out on horse-back now; thou lookest pale and emaciated, having lost all animation. I wish to know the disease thou sufferest from, so that I may endeavour to apply a remedy.' Thus addressed by his son, Santanu answered, 'Thou sayest truly, O son, that I have become melancholy. I will also tell thee why I am so. O thou of Bharata's line, thou art the only scion of this our large race. Thou art always engaged in sports of arms and achievements of prowess. But, O son, I am always thinking of the instability of human life. If any danger overtake thee, O child of Ganga, the result is that we become sonless. Truly thou alone art to me as a century of sons. I do not, therefore, desire to wed again. I only desire and pray that prosperity may ever attend thee so that our dynasty may be perpetuated. The wise say that he that hath one son hath no son. Sacrifices before fire and the knowledge of the three Vedas yield, it is true, everlasting religious merit, but all these, in point of religious merit, do not, come up to a sixteenth part of the religious merit attainable on the birth of a son. Indeed, in this respect, there is hardly any difference between men and the lower animals. O wise one, I do not entertain a shadow of doubt that one attains to heaven in consequence of his having begotten a son. The Vedas which constitute the root of the Puranas and are regarded as authoritative even by the gods, contain numerous proof of this. O thou of Bharata's race, thou art a hero of excitable temper, who is always engaged in the exercise of arms. It is very probable that thou wilt be slain on the field of battle. If it so happen, what then will be the state of the Bharata dynasty, It is this thought that hath made me so melancholy. I have now told thee fully the causes of my sorrow.' "Vaisampayana continued, 'Devavrata who was endued with great intelligence, having ascertained all this from the king, reflected within himself for a while. He then went to the old minister devoted to his father's welfare and asked him about the cause of the king's grief. O bull of Bharata's race, when the prince questioned the minister, the latter told him about the boon that was demanded by the chief of the fishermen in respect of his daughter Gandhavati. Then Devavrata, accompanied by many Kshatriya chiefs of venerable age, personally repaired to the chief of the fishermen and begged of him his daughter on behalf of the king. The chief of the fishermen received him with due adorations, and, O thou of Bharata's race, when the prince took his seat in the court of the chief, the latter addressed him and said, 'O bull among the Bharatas, thou art the first of all wielders of weapons and the only son of Santanu. Thy power is great.