During the tenth year of hijrah, young Ibrahim, who was then about a year and a half old, fell seriously ill. At the very time when the religion of the One was being established all over the Peninsula, with adversity constantly diminishing and the number of conversions continuing to grow, the Prophet, peace be upon him, saw his only son about to leave life and leave him. When the child eventually breathed his last, the Prophet took him in his arms and held him against his breast, tears streaming down his face, so deep was his sorrow.
The Prophet was intimately affected, and he did not hesitate to show and express his grief. He added: "The eye sheds tears, O Ibrahim, the heart is infinitely sad, and one must only utter what satisfies God." God had once more tested him through his humanity and his mission. He had lost so many loved ones - Companions, his wife Khadijah, three of his daughters, and his three sons. His life had been crossed with tears, but he remained both gentle with his heart and firm in his mission. It was this chemistry of gentleness and firmness that satisfied the Most Near. At the time when the world seemed to open up to the Prophet's mission, Muhammad's human fate seemed reduced to that tiny grave where Ibrahim's body was laid, and over which he then led the funeral prayer. The Prophet was one of the elect; the Prophet remained a human being.
"In The Footsteps of The Prophet" - Tariq Ramadan, pp. 191, 192