The questions are:
- King Kalmashapada, who was of the race of Ikshvaku, had an altercation with Sakti, the eldest son of Sage Vasistha. Sakti, who was himself a great ascetic, cursed Kalmashapada, to become a Rakshasa subsisting on human flesh!
Later at the behest of Sage Viswamitra, a raakshasa entered into the body of King Kalmashapada, who slew Sakti and other sons of Sage Vasistha and ate their flesh.
Sage Vasishtha, learning that all his sons had been caused to be slain by Viswamitra, patiently bore his grief like the great mountain that bears the earth. That best of Munis, that foremost of intelligent men, was resolved rather to sacrifice his own life than exterminate (in anger) the race of Kusikas.
After he failed in his suicide attempts, he returned to his hermitage. When he was about to re-enter his asylum, he was followed by his daughter-in-law named Adrisyanti. As she neared him, he heard the sound from behind of a very intelligent recitation of the Vedas with the six graces of elocution.
Hearing that sound, the Rishi asked, 'Who is it that followeth me?'
His daughter-in-law then answered, 'I am Adrisyanti, the wife of
Sakti. I am helpless, though devoted to asceticism.' Hearing her,
Vasishtha said, 'O daughter, whose is this voice that I heard,
repeating the Vedas along with the Angas like unto the voice of Sakti
reciting the Vedas with the Angas?'
Adrisyanti answered, 'I bear in my womb a child by thy son Saktri. He
hath been here full twelve years. The voice thou hearest is that of
the Muni, who is reciting the Vedas.'
'Thus addressed by her the illustrious Vasishtha became exceedingly
glad. And saying, 'O, there is a child (of my race)!'--he
refrained, O Partha, from self-destruction.
The reason for Sage Vasistha's attempting for suicide was the knowledge of slaying of all his sons by King Kalmashapada. The reason for his failure in committing suicide was, unknown to him, his grand son was taking life in his mother's womb. So there was no reason for his committing suicide. That was why he failed in his attempts to commit suicide.
Mahabharata was silent on who saved him from his suicidal attempts. We can infer that the Divine ascetic power, attained by Sage Vasistha, made him fail in his suicidal attempts, as he had to nourish his grand son, Parashara.