Tah'neek

One of the manifestations of the deep devotion the Companions radhiyallahu
anhum  had for the Prophet sallallahu alayhi wasallam  was that when a child was born in their family, they brought it to him so that he might bless it, and apply on its palate, the pulp of date etc., he had chewed himself and drop the saliva in its mouth, which they believed would have the effect of averting evil from the child and bringing it good fortune. It is called Ta'hneek in the Islaamic parlance.
Aa'ishah radhiyallahu anhaa  narrates:
"People used to bring their (new-born) children to the Apostle of Allah sallallahu alayhi wasallam , and he would bless them and perform Ta'hneek."

Muslim

Asmaa Binte Aboo Bakr radhiyallahu anhumaa relates that she was in the family way at the time of migration. When she migrated and came to Madeenah Munawwarah, Abdullah Ibne Zubayr radhiyallahu anhu was born to her. She relates that, "I took the child to the Apostle of Allah sallallahu alayhi wasallam  and placed it on his lap. The Prophet sallallahu alayhi wasallam  asked for a date, (and when it was brought), he chewed it and dropped the saliva in its mouth, and then applied the chewed date on its palate, and after it, he blessed the child. It was the first child to be born in Islaam (in the home of an emigrant, after the migration )."

Bukhaari, Muslim

Commentary:
In another version of the same incident, quoted in Bukhaari, it is added that the Muslims felt very happy at the birth of Abdullah Ibne Zubayr radhiyallahu anhu, particularly because it had gone round that the Jews had cast a spell on the Muslims, and now no children would be born to them. The birth of Abdullah Ibne Zubayr radhiyallahu anhu gave a lie to it, and the enemies of Islaam who had circulated the story were put to shame.

Several instances of Ta'hneek are found in the standard collections of the Traditions. From these, we learn that when a child is born in a Muslim home, it should be taken to a virtuous bondsman of Allah to receive his blessings and have the Ta'hneek done. It is one of the Sunnah which has now sadly become extinct.

Aqeeqah