Yunus (peace be upon him) remained in the belly of the whale for forty days

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he said: "Yunus (peace be upon him) remained in the belly of the fish for forty days."

It is narrated from Hasan al-Basri (may Allah have mercy on him) that he was asked about the saying of Allah Almighty: "And had he not been of those who glorify (Allah)" [Surah al-Saffat: 143], and he said: "What it means is that he used to pray abundantly in times of ease."

It is narrated from Imam al-Sha'bi (may Allah have mercy on him) that he said: "The fish swallowed Yunus bin Matta (peace be upon him) at forenoon (duha) and cast him out in the evening of the same day."

It is narrated from Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him) that he said that the Prophet (peace and blessings be upon him) said: "Whoever makes the supplication of Yunus (peace be upon him) which he made in the belly of the fish, his supplication will be answered."
This is a corroborating report (shahid) for the preceding hadith.

It is narrated from Wahb bin Munabbih (may Allah have mercy on him) that he said: "Yunus bin Matta (peace be upon him) was a righteous servant, but there was a harshness in his nature. So when the heavy burden of prophethood was placed upon him, and it has burdens that only a few people are able to bear, he was crushed beneath that burden just as a weak animal is crushed under a load. So he put that (responsibility) down from his hands and ran away from there. Allah Almighty says to His Prophet Muhammad (peace and blessings be upon him): 'So be patient, as the messengers of firm resolve were patient.' [Surah al-Ahqaf: 35] And He said: 'So be patient with the decision of your Lord, and do not be like the man of the fish (Yunus, peace be upon him), when he called out while he was filled with grief.' [Surah al-Qalam: 48] That is, do not abandon My command the way he abandoned it."