In the Hindu faith, Hanumaan and Ganesh are the two Devtaa who are not afflicted by Shani. There is also a belief that all the planets are under the control of Hanumaan's tail. Whoever worships Hanumaan is granted fortitude and strength.

Hanumaan has the rare Var or blessings from Shani Dev. As everybody knows, Raavan had won Tri-Lok and got a Var to be almost immortal. So Raavan had won all the Nine Planets also. He put these Nine Planets as a stair case to climb up on them daily to his throne. He felt a specific joy when he climbed on to his throne stepping on their back.

Hanumaan Saves Shani from Raavan OR
Why Worship Hanumaan on Saturday in Shani's Dashaa

In the Raamaayan, Hanumaan is said to have rescued Shani, that is the planet Saturn, from the clutches of Raavan. Raavan had become invincible because Shiv and Brahmaa's boons. So he had defeated all Devataa and Lokpaal and kept then under his foot. This made all Devtaa and Lokpaal very sad. They could not do anything, but Shani told them he might help them. Raavan was a great astrologer. When Raavan's son Meghnaad was born, Raavan put all his Graha in his 11th House so that he could also be invincible and immortal. Devtaa were very afraid of this and looked at Shani. So Shani stretched his leg a little bit from Raavan's clutches towards his 12th House. Raavan knew that this will cause Meghnaad's death, so he imprisoned Shani in a dark tiny cell so that nobody could see Shani's face again.

After some time, when Hanumaan was searching for Seetaa, he heard Shani's cries from a deep place. When Hanumaan looked here and there, he found Shani imprisoned in a cell. He requested Hanumaan to free him. Hanumaan freed him, but as he freed him, Shani looked at him and thus Hanumaan became the victim of Shani's gaze. Everybody knows that Shani's gaze is not good. Thus Hanumaan had to bear some hardships*, but at the same time Shani promised him that he would help him to degrade Raavan. In gratitude, Shani promised Hanumaan that those who would pray to him (Hanumaan) on his day (Saturday) would be rescued from the painful effects of Saturn, which in Hindu astrology, is said to produce malefic effects on one's life when one is afflicted "negatively" with Saturn. (read Shani and Raavan). Besides when Hanumaan was burning Lankaa, he found that he was not able to burn it properly. Then as Shani promised to Hanumaan to help him in degrading Raavan, he looked at Lankaa and turned it into black instead of a heap of gold.

* Here is another version
It is the divine scheme of things and no one can escape from it. Hanumaan wanted to know what sufferings he will have to face. Shani explained that "first I will come upon your head and this will make you leave your home, wife and sons and go about suffering. Hanumaan said that Shani can definitely come upon his head and as he has no family he will not suffer much with regard to his family and since his abode is at the feet of Lord Raam, he was assured that he would be able to tolerate that suffering also. So Shani took refuge on Hanumaan's head. Hanuman then began to fight the demons that chased him in Lankaa. In the process Hanuman had to carry heavy boulders, trees and rocks on his head. He crushed huge rocks with his head. Shani was getting hurt and suffering in the process. Finally, Shani got away from Hanumaan's head and said that you are the only one who will have no effect of my inauspiciousness. I cannot trouble you. Since you have saved me from Raavan's prison I would like to give you a boon. As the boon, Hanuman asked Lord Shani not to trouble or cast evil eye on his devotees. Lord Shani promised not to trouble or cause hardships to Hanuman devotees. That is why who worship Hanumaan on Saturday are not affected by Shani's Dosh.

Shani Troubles Hanumaan

Another encounter between Lord Hanuman and Shani Bhagavaan is that once Shani climbed on to Hanuman's shoulder, implying that he (Hanumaan) was coming under the effects of the influence of Shani. At this, Hanuman assumed a large size, and this made Shani caught between Hanumaan's shoulders and the ceiling of the room they were in. As the pain was unbearable, Shani requested Hanuman to release him, promising that if a person prayed to Hanumaan, he (Shani) would moderate the malefic effects of his influence on that person; following this, Hanuman released Shani.

Shani Troubles Hanumaan Again /
Why Mustard Oil is Given on Saturday?

You must have seen that many people give or donate some mustard oil on Saturday. Why do they do it?

When Shree Raam was building the bridge from Raameshwaram to Lankaa to cross the ocean for His army, Hanuman had the responsibility of looking after the security of bridge lest the enemy damage it. One day Hanumaan was sitting under a tree and was offering his prayer to God Raam, that Shani Dev came there and said to Hanumaan - "I am the most powerful god Shani Dev. I heard you are also so powerful, so I want to test your might with me. Open your eyes and fight with me."

In response to Shani Dev's challenge, Hanumaan opened his eyes and said - "Presently I am meditating upon my Lord. I request you not to disturb me in my prayers and leave me alone for some time." But Shani Dev was adamant on picking a fight. At the same time, Hanumaan stretched out his tail and started binding it around Shani Dev. Slowly he tightened his coiled tail and Shani Dev felt the tight grip around him. He tried to free himself from that grip but he could not. Hanumaan moved his tail up and down hitting him against the stones of the bridge. Shani Dev started bleeding.

When the pain was unbearable, Shani requested to him - "Release me. I will never do a similar mistake again." Hanumaan replied - "If you promise me that you shall never afflict Raam's devotees then only I will let you go." In the great pain Shani Dev had to promise to Hanumaan, "I will do as you say, I will never interfere in the destiny of those devoted to you and Raam. Please let me go." Hanumaan loosened his tail's grip and Shani got freed.

When Shani Dev became free, he asked Hanuman - "Could you give me some oil to relieve my this wretched pain?" Then Hanuman gave him some mustard oil to Shani Dev, after the massage of that oil on his body, his pain was relieved immediately. Since then it has been customary to offer some mustard oil in the name of Shani Dev. It is symbolic to sooth his pain. He feels satisfied and this makes him benevolent towards the devotee of Raam.

There is a spiritual interpretation of the relation between Hanumaan and Shani. Hanumaan is said to be a symbol of selflessness, while Shani is symbolic of ego and pride. Thus, to counter the Karm borne out of selfish action, one must be humble like Hanumaan. This is particularly true for those who are said to be experiencing the evil effects of Saadhe Saatee - a period of about seven and half years when Shani (Saturn) is supposed to afflict the three signs - one in which the Moon is placed in the natal chart of a person and the two house around it. One must be humble to all elders with a service feeling to them during that period.

Shani has troubled Hanumaan several times and each time he is defeated. This is another story when Shani came to trouble to Hanumaan. Although Hanumaan also had to go through Shani's Saadhe Saatee like all other beings, but Shani could do very little to afflict him. One story goes like this, that once Shani asked Hanumaan - "You are so powerful, what part of your body can I afflict?" Hanumaan said - "Sit on my tail." Hearing this Shani sat on his tail. When he did so, Hanumaan flipped his tail over him and pinned him to the ground so that he could neither move nor look at Hanumaan. Thus Hanumaan could save himself from Shani's affliction but later he did have to suffer a bit, when the portion of his tail that pinned Shani was set on fire by Raavan's people.

In another story, when Shani told Hanumaan that his Saadhe Saatee was going to begin, Hanumaan asked - "Which part of my body do you intend to live in?" Shani said - "I want to sit on your head." Hanumaan said, "Very well." When the first day of Hanumaan's Saadhe Saatee came, Shani Dev seated himself on the head of Hanumaan comfortably. Now Hanumaan began to play a little game. He would take a heavy mountain and throw it high in the air and let it fall on his head. After a few minutes, when Hanumaan had just started to enjoy this game, Shani cried - "Stop, Let me go, I leave you alone." Hanumaan asked smilingly - "You mean that you have had enough?" Shani replied - "Yes, I have had enough, but at least I made you hit your own head."