After coming back to the country he took part in the campaign of smoleński's king Władysław IV. During this trip on city Biała an event occurred, which had an impact on Jakub's future life- when he was buried alive in the trench he vowed that if he was to be survived he would with every strength propagate God's fame and he would built the church in honour of The Holy Trinity and St. Francisco.

When Jakub Wejher survived he settled down and got married. For his numerous military contributions and engineering work he was prized with człuchowski and bytowski starosty, chełminski's castellan department and the department of malborsky's voivode. This caused that he became one of the most important senators. Most of his vows he fulfilled in 1643 by building St. Francisco church in the area of rzucewski's ancestral church goods. By the temple Wejher located town settlement called Wejherowsky Wola. Later he funded there Franciscan monastery and Calvary as well as he urged the king Jan Kazimierz for town privilege for his settlement called from that day Wejheropolis.

Jakub Wejher was married twice but his male ancestors died in childhood. Most of his property - especially rzucewsko-wejherowskie lands Radziwiłłowie inherited from whose hands Sobiescy got them.