The history of Sikh religion entered a new phase with the coming of Guru Arjan Dev Ji to Guru Gaddi. It was the result of his efforts that Sikhs were blessed with Harmandir Sahib Ji and numerous other places of pilgrimage. Not only that, the Sikhs got their first sacred and divine book when Guru Arjan Dev Ji compiled the Adi Granth Sahib. The Hindus had their Ramayana, the Muslims their Quran Sharif, the Christians their Bible, and the Sikhs their Guru Granth Sahib Ji.

A brief description of the activities and contributions of Guru Arjan Dev Ji is given as follows:

1. Construction of Sri Harmandir Sahib: Guru Arjan Dev Ji completed the work of construction of Amritsar and Santokhsar Sarovars after the expiry of Guru Ram Das Ji. Guru Sahib constructed Sri Harmandir Sahib in the midst of Amritsar Sarovar. Guru Sahib constructed a door each in all the four directions of Sri Harmandir Sahib. These four doors convey the message that Sri Harmandir Sahib is open to all the religions, castes and tribes without any discrimination. Guru Sahib told his followers that a pilgrimage to Sri Harmandir Sahib would bestow the benefit of 68 places of pilgrimage of the Hindus. In this manner, Sri Harmandir Sahib became one of the most sacred and important rebgious places.

2. Foundation of Tarn Taran: Guru Arjan Dev Ji founded the city of Tarn Taran as well. The city was founded in the heart of Majha region. It is also an important place of pilgrimage like Amritsar for the Sikhs. Guru Ji also constructed many other buildings and Sarovars.

3. Construction of Baoli at Lahore: On his tour to Lahore, Guru Arjan Dev Ji got constructed a Baoli in the Dubbi Bazaar. The Baoli soon became an important place of pilgrimage for the Sikhs of the surrounding region.

4. Foundation of Hargobindpur and Chheratta: Guru Arjan Dev Ji founded the city of Hargobindpur on the banks of river Beas to celebrate the birth of his son Hargobind Ji. Apart from this he also got a well dug at Chheratta near Amritsar in order to provide water to the local people. Guru Sahib also arranged for six pulleys to draw Water from the well and the area is known after those pulleys as Chheratta.

5. Foundation of Kartarpur: In 1593, Guru Arjan Dev Ji founded the city of Kartarpur and also built a Sarovar in Kartarpur which is called Gangsar.

6. Improvement in the Masand System: Guru Arjan Dev Ji felt the need to improve Masand system. Guru Sahib instructed the Sikh followers to deposit one-tenth (Daswandh) of their annual income with the Masands. The Masands deposited the collections in the main treasury (Guru Ki Golak) at Amritsar on every Baisakhi day. The Masands appointed their representatives to collect donations. Those representatives were called Sangatias. The one-tenth donation was called Daswandh. Apart from the work of collection of Daswandh, the Masands also spread the message of Sikh religion.

7. Compilation of the Adi Granth Sahib: Gum Arjan Dev Ji bestowed upon the Sikhs a sacred and religious book by compiling the Adi Granth Sahib. Guru Ar^an Dev Ji compiled Adi Granth Sahib at Ramsar. Bhai Gurdas Ji assisted Guru Sahib in its compilation. The work of compilation was cofnpleted in 1604. Guru Sahib included the hymns of first four Gurus, followed by the hymns of Bhakti saints and finally the sayings of Bhatt Bahiyan. Guru Arjan Dev Ji also included his own Bani in the holy book.

8. Encouraged Horse Trade: Guru Arjan Dev Ji encouraged the Sikhs to start trading in horses. The Sikhs were benefited from the trading in horses in the following ways:

• Trading in horses was the most profitable business in those days. As a result, the Sikhs became very rich by trading in the horses. They contributed Daswand regularly out of their income from this trade.
• The Sikhs became fully trained in making a selection of good horses. It helped them in the long run in organising a Sikh cavalry.

9. Spread of Religious Teachings: Guru Arjan Dev Ji made many people his followers by his religious teachings. Guru Sahib impressed the people with his ideals, teachings, amiable personality, sweet temper, and toleration. Many Muslims also joined the Sikh religion under the influence of Guru Arjan Dev Ji.
Thus the Sikh religion progressed tremendously under the spiritual leadership of Guru Arjan Dev Ji. The Adi Granth Sahib, the most sacred book of the Sikhs, was compiled, the cities like Tara Taran, Kartarpur, Hargobindpur, were founded and the Sikh religion was blessed with Sri Harmandir Sahib.