Sai Mahabhakte Smt.Radhabai Deshmukh’s mention is made in Chapter 18 and 19 of holy Shri Sai Satcharitra written by Shri.Govind Ragunath Dabholkar alias Hemadpant.

Smt.Radhabai Deshmukh was an old woman. She was the mother of one Khashaba Deshmukh. Hearing Baba's fame, she came to Shirdi with the people of Sangamner. She took Baba's darshan and was much satisfied. She loved Baba intimately and resolved in her mind, that She should accept Baba as her Guru, and take some Upadesh from Him. She knew nothing else. She determined to fast herself unto death, so long as Baba did not accept her, and give her any Upadesh or Mantra. She stayed in her lodging and left off taking any food or water for three days. Shama was frightened by this ordeal of the old woman, and interceded with Baba on her behalf. Shama  said, "Deva, what is this You have started? You drag so many persons here. You know that old lady. She is very obstinate and depends on You entirely, She has resolved to fast unto death, if You don't accept and instruct her. If any thing worse happens, people will blame You, and say that Baba did not instruct her, and consequently she met her death. So take some mercy on her, bless her and instruct her." On seeing her determination, Baba sent for her, changed the turn of her mind by addressing her as follows:-

"Oh mother, why are you subjecting yourself to unnecessary tortures and hastening your death? You are really My Mother and I am your child. Take pity on Me and hear Me through. I tell you My own story, which if you listen carefully, will do you good. I had a Guru. He was a great Saint and most merciful. I served him long, very long; still he would not blow any Mantra into My ears. I had a keen desire, never to leave him but to stay with and serve him; and at all costs receive some instructions from him. But he had his own way. He first got my head shaved and asked Me two paisa as Dakshina. I gave the same at once. If you say that as My Guru was perfect, why should he ask for money and how should he be called desireless? I replied plainly that he never cared for coins. What had he to do with them? His two paisa were (1) Firm Faith and (2) Patience or perseverance. I gave these two paisa or things to him, and he was pleased.

"I resorted to My Guru for 12 years. He brought Me up. There was no dearth of food and clothing. He was full of love nay, he was love incarnate. How can I describe it? He loved Me most. Rare is a Guru like him. When I looked at him, he seemed as if he was in deep meditation, and then we both were filled with Bliss. Night and day, I gazed at him with no thought of hunger and thirst. Without him, I felt restless. I had no other object to meditate, nor any other thing than My Guru to attend. He was My sole refuge. My mind was always fixed on him. This is one paisa Dakshina. Saburi (Patience or perseverance) is the other paisa. I waited patiently and very long on My Guru and served him. This Saburi will ferry you across the sea of this mundane existence. Saburi is manliness in man, it removes all sins and afflictions, gets rid of calamities in various ways, and casts aside all fear, and ultimately gives you success. Saburi is the mine of virtues, consort of good thought. Nishtha (Faith) and Saburi (Patience) are like twin sisters, loving each other very intimately."

"My Guru never expected any other thing from Me. He never neglected Me, but protected Me at all times. I lived with him, and was sometimes away from him; still I never felt the want or absence of his love. He always protected Me by his glance, just as the tortoise feeds her young ones, whether they are near her or away from her on the other side of the river bank, by her loving looks. Oh mother, My Guru never taught Me any Mantra, then how shall I blow any Mantra in your ears? Just remember that Guru's tortoise-like loving glance gives us happiness. Do not try to get Mantra or Upadesh from anybody. Make Me the sole object of your thoughts and actions; and you will, no doubt, attain Paramartha (the spiritual goal of life). Look at Me whole-heartedly, and I in turn look at you similarly. Sitting in this Masjid, I speak the truth, nothing but the truth. No Sadhanas, nor proficiency in the six Shastras, are necessary. Have faith and confidence in your Guru. Believe fully, that Guru is the sole Actor or Doer. Blessed is he who knows the greatness of his Guru and thinks him to be Hari, Hara and Brahma (Trimurti) Incarnate."

Instructed by Baba in this way, the old lady Smt.Radhabai Deshmukh was convinced; she bowed to Baba and gave up her fast (Ref: Shri Sai Sactcharitra Chapter 18 and 19)

Smt.Sarayu Ranjit Deshmukh who is a resident of Sangamner and Great Grand Daughter of Smt.Radhabai Deshmukh and her Husband Shri.Ranjit Deshmukh are also staunch devotees of Shri Sai Baba and following the legacy left by Smt.Radhabai Deshmukh.

Smt.Sarayu Ranjit Deshmukh narrated in her own words Shri Sai Satcharitra experience which was published in Shri Sai Leela Magazine May-June 2012 issue as follows:

“I, Smt. Sharyu Ranjit Deshmukh would like to narrate my Sai-charitra Experience. For me, Sai-charitra is Kripa Prasad. Baba could virtually reach to me through Sai-charitra. Dreams are a common factor in any human being's life. But Baba's darshan in a dream was in a true sense a revelation to me. Baba told me to bring his padukas to my home and coincidentally the next morning my close friend Mrs. Savita Bhandari invited me for lunch with Sai-devotee Shri Ingle. Shri Ingle gifted me the most valuable and precious Sai-charitra. I will never forget that lunch and gift of Sai-charitra throughout my life. And to my pleasant surprise, my husband Shri.Ranjit Deshmukh too received a copy of Sai-charitra by way of a gift. The existence of Sai-charitra in our home itself is a certainity of happiness and prosperity. I often wished if I could climb up the chouthara and take Sai-darshan, but this was not possible. But Sai turned the impossible to possible by giving me darshan in my dreams the way I wanted”.

“My great grandmother Radhabai Deshmukh was a staunch Sai-devotee. You will find her reference in the 18th and 19th chapter of Shri Sai-charitra. She had made a resolution to herself to take guru-mantra from Sai-Baba. She observed a severe fast to obtain the guru mantra. Finally Baba gave her only in two words the guru-mantra, 'Shraddha and Saburi'. Today, these two words of Baba are famous all over the world as 'Sai updesh'. I consider my arrival in Deshmukh family and devotion and love over Baba as the next generation of my great grandmother in Deshmukh family”.

“Distance does not matter for Baba; he is always with his devotee. I often visit Shirdi for darshan; otherwise I visit the Sai temple every Thursday and take darshan. I forget all my grief, troubles and distress at Sai-Baba's feet. The spiritual happiness which I derive from Sai-darshan is priceless. I once again bow down to Sai Baba”.

(Source: Shri Sai Satcharitra Chapter 18 and 19 and Shri Sai Leela Magazine May-June 2012)